Beauregard

At higher levels, most villain groups carry significant defense debuffs. So without defense debuff resistance, what you'll discover is that the soft-capped S/L you're so proud of will vanish in an eyeblink if you jump into battle because S/L doesn't protect against most of those debuffs (they tend to be toxic, psionic or have huge accuracy bonuses against S/L).

Even excluding defense debuffs, the return on S/L defense is extremely low since Electric Armor already has such outstanding resists vs. S/L. When you're only taking 10% damage from a damage type, spending serious effort to cut it down further isn't all that useful.

If you want to invest in a defense category, go for Ranged defense. Electric Armor's weak spots are Psionic, Toxic and Negative. Almost all of those attacks are delivered at range.

You may not want to hear it, but the first step would be to switch archetypes.

The value of a Corruptor over a Defender is more damage. But due to the -resist debuffs on both Thermal and Sonic being larger for Defenders rather than Corruptors, you're losing most of the damage advantage of a Corruptor.

The Defender version would also heal more and buff better. The Defender version would also be more survivable due to the superior +def from pools. The Defender version even has a more elegant leveling structure (top end Thermal powers are essential; top end Sonic Blast powers aren't).

Dark Melee doesn't have much AE, but it does have Soul Drain (a better version of Rage for your purposes) and you can just grab Mu Mastery if you wanted AE.

The problem you're experiencing is what is termed a 'cascading defense failure'. You're facing off against a host of enemies that fire off a volley of -defense debuffs, your defenses go into the negatives and then they follow up with attacks that strike against your weakest resists. It's one of the reasons many players (mistakenly) view resist sets as being 'squishy' when they get to higher levels.

Nor will Defensive Sweep help you much. The attacks you're worried about are Ranged/Psionic attacks. So building up your Smashing/Melee defense merely means that you'll end up with slightly less negative Smashing/Melee as they punch through your relatively weak Ranged/Psionic with ease. Indeed, you'll probably discover that Smashing/Melee defense is generally not very useful for a resist-based melee because you've already got fantastic resists against those attacks.

Your basic intuition about positional defenses is correct: ranged defense is really what you need, since most of the attacks you're really concerned about are ranged. As an Electric tank, you have three weak resist categories: Psionic, Negative and Toxic. Almost every attack of those types is ranged. It may seem counter-intuitive to stress ranged defense in a melee build, but keep in mind that an attack remains 'ranged' even when used from point-blank range.

Beyond this, some ways of dealing with your problem:
1. Sapping. Electric Armor has two 'sapping' powers - Lightning Field and Power Sink. Power Sink alone will rip away over half the endurance of +3 (+4 with level shift) minions/lieutenants. Lightning Field isn't quite as dramatic, but enemies within your Lightning Field will quickly lose the remainder and then only attack intermittently.

2. Epic powers. Prior to AOs, I would have suggested Mu Mastery. However, post-AO (and possibly even pre-AO) I'd say go with Soul Mastery. Soul Mastery gives you one of the best single target attacks available to Brutes (Gloom) as well as the ability to blanket the entire spawn with -to hit before you engage with Dark Obliteration. If you really want to nail it home, you can add Darkest Night to the mix. Soul Mastery transforms the problem of soft-capping Ranged (and other defenses) from an impossibility to merely a difficulty.

There are other possibilities as well - arguments could be made for Earth or Arctic Mastery. However, the one epic pool I wouldn't take just so happens to be the one you did - Energy Mastery. Electric Armor gives you nearly infinite endurance and a self-heal, so really all you get from Energy Mastery is an endurance-intensive accuracy toggle that you probably won't need.

3. AE Knockdown. Obviously, AE Hold or AE Disorient would work just as well - but you don't have those options. AE Knockdown, whether from the primary or even Spring Attack, means that you can negate the alpha strike of -defense debuffs. While this merely delays the inevitable, you just need to buy enough time to drain their endurance.

4. Inspirations/Incarnates/Accolades. There are various ways to get a brief period of either soft-capping defense or being really, really tough. Unfortunately, these all involve either long cooldowns or consumables so they're your last choice. Burnout would also fit into this category, since it allows you to toss two Power Sinks, two Energizes and/or two control effects in a row (on a long cooldown at a steep end cost).

Ring of Fire. This is frequently skipped because Ring of Fire recharges so quickly and an additional attack normally isn't needed.

Transfusion. This needs to be slotted for accuracy as well.

Char. In Fire/Kinetics, you generally slot this as a Hold rather than Damage since you'll have such significant damage boosts anyway.

Hasten. With enhancement boosters, you really only need to 2-slot this.

Cinders. I normally skip this since having a long recharge mass Hold isn't really much better than a long duration mass Disorient.

Stealth. This is worthless if you've got Celerity/Stealth and Super Speed.

Boxing. Controllers frequently slot this with sets like Mako's Bite because it's actually not that bad an attack for a Controller (on Contained targets).

Inertial Reduction. This is a rather strange choice. No one else is likely to need Superjump, and it's an annoying way to provide it for yourself.

I'd also question taking Fire Mastery. If you took Mu Mastery, you'd get basically the same AE performance, a better set of resists from the armor, a nice defensive 'panic button' and a pet you can use to slot all 4 of the "keep my Fire Imps from insta-dying" enhancements.

Some things to contemplate taking:
Siphon Speed. This isn't all that great when you're just plowing through large spawns, but is nice against single hard targets to make your rotation run a bit smoother.

Tactics. 6-slot Gaussian is one of the easiest ways to boost defense and Kinetics is such a accuracy-dependent set that having better hit chance is essential.

Vengeance. This is a nice mule for Luck of the Gambler if you've already got enough Leadership powers.

The arcanatime-adjusted dpa for each Blaster attack:
Snap Shot = 44.23
Aimed Shot = 46.31
Fistful of Arrows = 43.13
Blazing Arrow = 81.68
Explosive Arrow = 47.40
Ranged Shot (90% int. red) = 52.32
Rain of Arrows = 53.32

Snap Shot and Aimed Shot are horrible compared to the average Tier 1/2 Blaster attack. Blazing Arrow is middle-of-the-round for heavy single target Blaster attacks. This yields the rather non-intuitive result that the best single target rotation for a Blaster Archer includes neither Tier 1/2 attack. You wouldn't even take them if you weren't forced.

The AE damage is still acceptable, but having garbage Tier 1/2 attacks doesn't work all that well with Defiance. So it's hard to recommend Archery for a Blaster.

For Corruptors:
Snap Shot = 23.87
Aimed Shot = 35.11
Fistful of Arrows = 28.75
Blazing Arrow = 55.20
Explosive Arrow = 31.59
Ranged Shot (90% int. red) = 34.88
Rain of Arrows = 35.15

Snap Shot is awful, but Aimed Shot is actually worthwhile for Corruptors.

Note that in both cases, Rain of Arrows is rather uninspiring. It's only slightly more dpa than conventional AE attacks and roots you for 4 sec. Unless you're using it to alpha strike a group (a tactic that fades quickly once you start fighting things that will just turn around and kill you in response), it's not normally worth taking.

Trick Arrow isn't all that great of a buff/debuff set. Like all debuff sets, it runs into issues when you scale up the difficulty of the content. Unlike other debuff sets, it has nothing but debuffs. Essentially, by the time you get the kind of abilities that really make a difference they no longer make a difference.

A better choice would be a set like Cold that has minimal activity during combat itself, good slotting opportunities and operates entirely from range.

Snipes in general aren't worthwhile since they take an enormous amount of time to animate, are interruptible and don't deliver enough damage given their animation time.

That being said, Radiation Blast for Corruptors/Defenders is an unusual case because the first two nukes are horrible. The merely mediocre performance of Proton Volley makes it a better choice for your rotation than X-Ray Beam or Neutrino Bolt.

X-Ray Beam and Neutrino Bolt are, in fact, so terrible that they lose out to four pool attacks: Electric Fence, Dominate, Boxing and Air Superiority. If you have any of those four abilities, they should take the place of using either of Radiation's first two blasts in your rotation.

The rest of your rotation would be Cosmic Burst and either Irradiate or Proton Volley depending on whether you preferred fighting at range or up close. Note that the Irradiate rotations are higher damage than the Proton Volley ones.

The highest dps rotation using only Radiation Blast nukes would be Irradiate + Cosmic Burst + Proton Volley. However, this rotation is a bit sketchy since you're combining a PBAE and an interruptible attack.

Note that this is not true for the Blaster version of the set and I don't believe there's another blast set in the game where you'd get similar results.

Enhancing the endurance return is less effective than enhancing endurance reduction.

More importantly, I think you're going the wrong direction with that build. */Kinetics doesn't need to slot for endurance reduction because it has Transference. You should 6-slot it with accuracy, endurance modification and recharge reduction.

Once slotted up, Transference will restore your entire endurance bar in one fell swoop - and it comes up often enough that it's tough to outspend. It's also the single most devastating 'sap' ability in the game. A Corruptor's fully slotted Transference drains over 100% of the target's endurance (ie: all of it).

What you might stop to consider for a moment is that you generally want your primary power set to be the one you use primarily.

Which isn't the case with Force Field. You've got some target-ally buffs you use every 2 minutes or so, a toggle buff you just leave on all the time and a bunch of knockback/repel powers you probably won't even take. It's a power set that screams 'secondary'.

So if you were to play such a character, you'd ordinarily want to play a Beam Rifle/Force Field Corruptor (rather than Defender). Since you can't, may I recommend the next best thing: Beam Rifle/Sonic Corruptor?

Sonic Resonance gives you the same benefit as Force Field for personal defense. Resistance is actually better than Defense for your purposes since you'll already have the status protections. Sonic Resonance also gives you -resistance debuffs to increase your damage. But Sonic Resonance is still a 'bubble' set that is mainly long duration fire-and-forget powers that won't interfere with blasting away.

Radiation Emission was bugged for a while meaning that it's debuffs didn't suffer the resistances that the debuffs from other sets did. So it was overpowered until they fixed it (which they did). Now its debuffs are on the same level as any other.

In terms of the whole set being "great for AV/GMs", it depends on what you're talking about.

If you're talking about solo'ing AV/GMs, the answer is yes. Debuff-intensive sets tends to be great for solo'ing tough content because almost all of the best buffs can't be used on the player themselves.

If you're talking about teams going after AV/GM, it's a completely different story. The purple patch will halve the effectiveness of debuffs on a +4 AV/GM. The AV/GM resistances will reduce that even further - you'll only be getting 15% of the return on most debuffs. So your -resistance debuff is only worth half what a comparable +damage buff would be worth and your -defense debuff is worth about 1/16th of a +hit buff.

The main value of Radiation in a team AV/GM fight is actually Accelerate Metabolism. AM is a solid buff, but it's not really up to the standards of 'buff other' benefits like Forge. So Radiation Emission would end up in the middle of the park. It's better than pure debuff/control sets like Dark, but worse then pure buff/heal sets like Thermal and Pain.