Hopeling

Your math isn't correct, by the way.

Brutes, at their cap, are basically dealing
.75 * 7.75 = 5.8125 damage mod
If you want 90% of that, that would be 5.23 damage mod.
With a Tanker's base damage mod of .8, that would be 654% damage, or 650% if you wanted a rounder number. As in, base damage + 95% enhancement + double Rage + 275% headroom. So your math is short by about 100%.

But, I don't think a 650% damage cap is a good idea, because I don't think the 10% difference in survivability you're citing is a valid mirror to the damage cap. Even putting aside my objections on the matter as a whole for a moment, getting massive damage buffs is so incredibly much more common than getting massive resist/hp buffs that it seems quite unfair (in the other direction) for Tankers to deal 90% as much damage as Brutes at their cap, which they can reach quite often, but the conditions that get a Brute to their defensive caps so they can be 90% as tough as a Tanker are almost vanishingly rare (especially the HP cap, for Brutes that aren't /Invuln, /Regen, or /Stone).

If the Tanker damage cap were to be raised, I'd say 500% was more reasonable, and also has the benefit of being a) a nice round number and b) on par with the other ATs that have higher-than-normal caps and aren't Brutes. I don't think raising the damage cap would really address the core complaints players have about Tankers, though - not even your own complaints, really - or at least, it wouldn't do much by itself. Along with some changes to other things, maybe, sure.
No, the gap is wider than that. Brutes have 75% the base values of Tankers, so if you flip it around as you stated, Tankers have 133.3% the base values of Brutes. (Granted, with IOs the gap becomes somewhat smaller, since set bonuses do not vary with AT modifiers.)

This sounds really interesting; what colors did you use, if you don't mind sharing? I tried it just now on beta and couldn't get anything I liked the look of.

Partly thanks to Incarnates, sure, definitely.

But, considering that the dozen-ish 50+3s I have by now all play quite differently, despite their Incarnate powers, I'm gonna go ahead and say that statements like this:
...are false. Laughably incorrect. Hogwash. Removing Judgement from my bar would obviously reduce the character's capabilities, but not by nearly as much as removing Fireball, or Assassin Strike, or Foot Stomp, or Crushing Uppercut, or (more relevant to this thread) Shatter, or Crowd Control. Removing Lore would affect me much less than removing Call Reinforcements and Summon Blaster. Et cetera.

Yes, that is why most (all?) of us in this conversation seem to agree that such changes should not actually happen, or at least should not be made lightly: the backlash from players who like things as they have been for years would be enormous.

That doesn't mean the design decisions that led here were all good ones, though.

On some builds, yes.

It's sort of a hack to get around the way that NPCs stay in the same place every hour of the day and night, rather than moving around the way actual people do.

Interesting, but it's still transferring all that heat into the target. If it made any difference at all (and I'm not sure the game really needs to model this particular quirk of physics, but just for the sake of discussion), more readily transferring energy would mean more damage, not less.