Ahoy thar, mt Rad/Kin is PvP based but i haven't used him in Sirens too much yet, and not at all in Warburg (wehre i think i'd be more effective). Anyway, just givin ya some background so you know where i'm coming from =D
Cosmic Burst is a disorient as you know, and thus acrobatics does *not* resist by itself, but of course you won't be able to mez Scrappers and Tankers etc. The damage on it (3 slotted with lev 40 damage SO's) is sufficient but may leave you slightly underwhelmed.
X-ray beam is a fantastic power, as the animation isn't too slow and the damage is pretty much what it says it is - 'moderate', as well as having a fairly short recharge time. However, as i'm usually debuffing when i'm not attacking you don't notice the recharge of powers so much when you can maintain an attack chain. I have found this particularly good for picking off Defianced Blasters.
I respecced out of the snipe (the name escapes me) as as you correctly assumed it's fairly useless in PvP. I think if it was more like the Energy snipe it'd be more effective as the hit is much quicker, but i only ever used it to *try* and pick off low-health runners, but it hardly ever reaches the target. If you get this, perhaps slot it for range more than damage, as you could easily pick off a low health and stationary target.
Neutrino Bolt - ya, skip it, the damage is useless and the quick recharge just doesn't cut it. And like you said, it doesn't chain well with X-ray beam.
Irradiate - I haven't had a chance to try this baby out yet, but in a zone where there's an innate -50% accuracy debuff anything that's going to improve that is going to be hella useful, i would imagine especially against SR Scrappers. Plus, the animation is short for a PBAoE.
Electron Haze, well, i specced into this because i needed another single target power in case i wanna attempt to solo someone (and yes, i know it's cone, but usually won't hit more than one target in a zone). The animation is very slow, and being rooted that long isn't pleasant, but i use it if none of my other powers are up and maybe there's a hole in my attack chain. Plus, with it's chance to knockback it can keep my opponent off balance when i combine it with Cosmic Burst and Repel. The recharge isn't too horrible, either.
Other than Atomic Blast those are really all the powers i took, as being a Kin obviously i have a lot of powers in my secondary. I haven't slotted AB at all yet, and won't before i7, as i put a lot of my slots in Transference and Fulcrum Shift, but i think it would be useful in a group situation where you may be able to jump in and hold all the squishies for awhile, not to mention debuff and damage them at the same time. Don't wanna focus on the damage though, but i'm a little biased with Fulcrum behind me :P
[ QUOTE ]
but in a zone where there's an innate -50% accuracy debuff
[/ QUOTE ]Actually, players just have 25% defence buff 
Whoops, my bad o.O
Whoops, my bad o.O
Aye, I agree with pretty much all you said there, except for perhaps taking electron haze. I've never used this power myself, but if it leaves you rooted for a long time I'd say dump it. Maneuverability counts for a lot in PvP. Irradiate should be handy, since it's a quick animation. The damage is pretty poop (and it's DoT) so I'd slot it for defence debuff and accuracy. You might just be able to get away with slotting 1 acc in your attacks if you slot irradiate 3acc 3def debuff. Maybe 
I'm pretty sure a rad/rad could get away with it, using radiation infection as well.
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CRUELY TAKEN FROM THIS WORLD WHILE SO YOUNG
This is always a thing on my mind when I think of Irradiator, and I'm thinking of remaking a PvP corruptor with this instead of Ice Blast, since it fits better with his costume and theme in general.
Question: what would you take?
Since rad is kinda better on the AoE side of things, it looks like you don't have that many powers to take. X-ray Beam or Neutrino Bolt (but never both, they don't chain well), Cosmic Burst and Aim and maybe, just maybe, Atomic Blast if you're feeling particularly insane. A possibility is Irradiate too, for the tasty defence debuff (slotted for that rather than damage). I can't see a snipe being useful for a PvP corruptor,
Cosmic Burst is an interesting one, it's got a shortish recharge time, fast animation, great damage and a good stun. Now, just for taking all those annoying acrobatics users you could slot this for stun rather than damage, stick with the damage or go with a compromise or 2 acc, 2 disorient, 2 damage. Since I don't think you've ever going to kill someone particularly fast with rad blast I'd be tempted to go with the compromise, but what would you do?
IN MEMORIUM OF GAYBABY
CRUELY TAKEN FROM THIS WORLD WHILE SO YOUNG