(I think this discussion should be in either the Characters or Suggestions and Feedback forums, but maybe since it would fit in either one, General is fine. Gah!)
I suggest D3 adopts a “tiny buff” approach. The problem with a big buff (power overhaul) is that you can go too far and then have to bring it back with a nerf, which players hate.
E.g. We decide that IM40’s yellow is too expensive, so we change it to

Recharge 8 AP
Creates 3 Countdown tiles that restore 3 Red AP each. Iron Man is stunned for 1 turn.
- Rank 2: Each countdown tile also restores 3 Blue AP.
Rank 3: Countdown tiles restore 4 Blue AP.
Rank 4: Countdown tiles restore 4 Red AP.
Rank 5: Creates 4 Countdown tiles.
… By almost any measure, this power is now much, much better. It doesn’t make as much AP but it makes more in the colors IM needs, and is much cheaper. Even so, if the devs made this change, somehow, a weirdly vocal contingent of protesters would inevitably pipe up and complain that the game is ruined now because IM40 can’t generate a couple Black AP.
SO, going back to the “tiny buff” approach, let’s just say Recharge makes one more CD tile, and after a month or two, see if people are using it a bit more heavily. No one can complain that it’s too different, since it’s strictly better, and I really doubt he’ll skyrocket in utility, forcing them to undo the change. Or if Ballistic Salvo is the power people hate more (I’m sure more people have it at 5 ranks than Recharge), boost the damage by 15% and see what people are saying. If they have to nerf it back down for some other option, well, we signed up for that.
So, other characters that could use a tiny buff?
Spider-Man (Classic): NONE. Seriously. He rocks PvE and, when he’s one of the weekly buffed characters, does fine in PvP.
Black Widow (Grey Suit): I think the only real problem people have with GSW is that she’s stuck with 3 Red (unless you hate winning). Making Sniper Rifle AoE at rank 4 would make 4/4/5 viable as well. She’s a powerful character in PvE and on offense, I’m not sure she needs a change, but making her red cheaper at ranks 4-5 would give those masochistic, winning-hating players a fighting chance.
Psylocke: Boost her tile strength by 25%. Or maybe less. But just see how she does a bit stronger. Psylocke was a very “fast” character, with a couple of cheap attacks to down a dangerous opponent (with bonus Strike/Attack damage) before they can get a shot off. Now that HPs have been boosted across the board, that strategy isn’t as effective.
Or, just make Bewilder steal random AP from different colors and it becomes super-keen.
Punisher: Tile strength! (see Psylocke, above). Boosted to 240, he feels about as good as a top-tier 166 character.
Hulk: Don’t kid. He’s still top-tier on 166 defense, especially when boosted. Doesn’t need a buff.
Wolverine (X-Force): Green should do +700 damage at rank 2 and above. I’m sitting on a 1/5/2 XFW, level 172. The next green cover increases his damage from 235 to 313. “Yay, I got a 4* cover, now I can do 78 more damage.” Spend 2500 
on that? No. Tinykitty. Way.
A boost to even 800 (so +565 at 172, more closer to 270) would make me much less ambivalent about it, and I don’t think people would be screaming for the ban-hammer since it’s still his weakest power.
Captain Marvel: A lot of my micro-buff suggestions target a hero’s weakest powers, but instead I’d suggest lowering her AP cost on black by 1. Man, that’d rock. But she’s a go-to when powered up so she probably doesn’t need a buff.
Rags: Let us sell covers in respec so I can leave him at 5/5/0 and use him as a blue generator for other characters. But more seriously, eh, up his green damage a bit? Or if Lightning Rod’s green tiles were added to the board (instead of just converted), you’d have a better chance at matching them than your opponent, which would help. Maybe that’s too big.
Storm (Mohawk): Oh, Storm, I miss the days when you were good. Still, she occasionally gets an AP roll going and stomps me on defense (TU is gain is nice for the AI who can have pretty decent ones). I think Yellow should destroy all TU tiles (but keep the limit on TU gained to 5 or 7). The damage increase could still encourage people to consider 4 or 5 ranks in Yellow. (For 9 Yellow, Black Panther makes 500 damage in Strike tiles, compared to this power’s pathetic 1500.)
Vision: Just code the AI so his modes don’t get priority unless they are 1 turn to vanishing, (or would create a match when relocating…). Let him stay in his modes for a while.
More: I’m tired now. You guys can chime in.