Hopeling

Originally, both of BotZ's set bonuses were much larger (3.13%, if I recall?). This was eventually reduced to the values it has now, and there was some outcry over it at the time, but as you may have noticed, we went on with our lives, and softcapped builds are as prevalent as ever.

OK, so it's adding 18 damage to Lunge. By comparison, a (non-purple) damage proc has a 20% chance to add ~70 damage, or ~14 damage per hit on average. And that would only be in the attack you put the proc in - a damage buff affects every attack.

Plus, it can stack.

Good point. A defense buff works against attacks from any enemy, but only for the character(s) buffed. A tohit debuff works against attacks only from the debuffed enemy/enemies, but benefits any character being attacked.

Not necessarily - unlike normal IO procs, the ATO procs have a higher proc chance in powers with longer recharge. So rather than putting it in your fastest-recharging power, or the power you use most often, you want to put it in a power that you use as often as possible, that is, as soon as it recharges. There's an upper limit on how long you want the recharge to be (where the proc rate reaches 100%, so a longer recharge stops raising it), so very long-recharge powers like Shield Charge are not good places for the proc. The exact cutoff point isn't clear yet, since we don't know the exact formula for the proc rate, but most non-nuke attacks should be below that point.

Well, the difference between 15% and 21% is small enough that it's very difficult to notice by just eyeballing it. It is definitely there, though, and it's roughly comparable to slotting a normal IO damage proc in every attack.

...and he's selling this item for far less than a Spider-Man #1 would fetch, which is consistent with its far lesser value as a collectible.

Whether you personally place value on it does not matter at all, because there really are people out there who collect such things. I don't know how many of them there are, or how much they care about this item specifically, or how much they'd be willing to spend on it, but they definitely exist.
Maybe his asking price is too high, it's hard to say except by just seeing if the item does or doesn't sell. There is hardly a stable market for this item, after all. But he is well within his rights, and entirely reasonable, to sell it, and ask for any price he thinks is fair for it. Either it will sell, or it won't, and your ridicule or disdain on the topic are unimportant.

It actually is the same: debuffing an enemy's tohit by 5% (or any other amount) is exactly equivalent to +5% defense (or any other amount), against attacks from that enemy.

But there's a couple wrinkles that can cause enemies to actually be debuffed by an amount other than what your debuff applies. The first is the Purple Patch, which will make your powers less effective against foes above your level. The second is Archvillain debuff resistance, which resists tohit debuffs.

So, your -30% tohit is just as good as +30% defense, against a non-AV enemy your own level. On the other end of the scale, a level 54 AV (with you at 50) would reduce your debuffs to .48 effectiveness (-14.4%), and then resist 87% of that, so your 30% debuff would only reduce their tohit by 1.87%.

Tohit debuff enhancements are schedule B, so you can get to ~56% enhancement before ED becomes severe. Slotting both powers to the ED cap would give you ~47% of tohit debuffs total, which will floor the hit chance of +0 non-AV enemies, even with no defense at all, but you'll need more debuffs or some defense if you want to be softcapped against higher foes.

Badge protection isn't very good as a "bonus" in the first place, so I totally agree.

...a scrapper?

If you mean ranged, though, some of the VEATs might be up your alley. I really like my Fire/Time corr, very strong all around, but it's not blaster-level damage.

If the fleeing was from situations they can't win, it would be less annoying. (Arguably that's most of the situations in the game, but...) But the fleeing has very little to do with their chances in the fight, and very much to do with certain effects being arbitrarily scarier than others. Your buddies getting eviscerated next to you: not scary. Somebody carrying a lighter: Very scary.

TOs are kinda weak. DOs definitely are not. This game is easy enough that you can get by without any enhancements until 22 if you want to, but equipping DOs at 12 definitely makes a difference.

I don't think that's a useful way to look at it, no. It's factually true, but it's not as useful for comparing "Dark Detonation with Posi's blast" vs "Dark Detonation with Kheld Grace". Saying "the Grace slotting lets me use the power 15% more often than the Posi slotting" (or whatever) is a more useful and applicable comparison, because it directly compares one slotting to the other (if I traded this Posi set for Grace, how many more Dark Detonations could I throw around? About 15% more), rather than comparing both to some third metric that never actually comes into play.
We often compare base damage values between different powers, because that's simple to compare and the ratio will be the same if both powers are slotted the same way. I don't think I've ever seen anyone compare two different slottings of the same power and talk about both slottings primarily in comparison to the base damage.
I don't think I have told you it doesn't have an impact. I certainly haven't intended to. My quote you replied to there said it usually has as little impact as the proportionally smaller change to a faster-recharging power: which is to say, most often not a lot of impact, but sometimes it can be significant, if it creates or removes a gap in your attack chain, or lets you switch to a better chain, or etc. But usually, a small difference in recharge, like from a single LotG, will not push you across such a breakpoint.

(Personally, I think perma-hasten is overrated as a goal in itself. I barely notice using a slightly worse chain for the 10 seconds every 130 while Hasten is down on most of my characters. If some other build goal also lies in perma-hasten territory, then that can be important. That's a bit of a tangent, though.)

If you want to compare the ATO set to Posi's Blast, you compare it to Posi's Blast, not an unslotted power. In that comparison, Grace comes out ahead by a little less than a second, out of a little more than five, which is a meaningful and noticeable difference, if not a dramatic one.

Comparing either set to the base recharge is not a useful or meaningful comparison, because leaving the power completely unslotted and using no global recharge bonuses wasn't even on the table.
I was not attempting to make any comparison, either, only an analogy that one choice can be "way better" than another, even if its total impact on the power or build as a whole is very small.

If you're going to use quote marks, implying an actual quote rather than paraphrasing, please do not leave out important words. I said "from most powers". Hasten and other powers with long recharges would be (I thought) obvious exceptions, and a couple seconds one way or the other on Hasten usually makes as little difference to a build as the proportionally smaller difference on faster-recharging powers, anyway.

Frankly, one second out of five is indeed a pretty large difference, especially when that's by simply swapping one set for the other, not spending additional slots or something. Your character as a whole may not be way better using the set, but the set's contribution to your character as a whole is indeed what I would call "way better". A LotG 7.5 will take off much less than a second from most powers, yet most people would probably agree that it's "way better" than a level 20 generic defense IO that grants about the same defense, but no recharge.

With the upgraded set, I think you might be able to leave out the dam/rech instead and still have ED-capped recharge, but I don't have the numbers in front of me right now so I'm not sure.

If you want the resistance, though, get that. My personal preference is for the proc, but the difference either way probably isn't huge when you've already got perma-hasten.

Recharge proc, IMO. No reason you can't do a recharge proc + 5 pieces of upgraded Brute's Fury, too.

...yes, I got that. I instead chose to derail his attempted insult.

With inflation, you could even say the price has really gone down.