Everything here would be personal opinion. There's no claim that what I say is the absolute right or wrong.
Now that I am able to recruit all the heroes (except Angel and Red Hulk at the time of writing) and I have used most of them a fair number of times, I think I have a good enough insight into their performance. I'd indicate if I haven't used the character that much. In any case, I'm no expert and your assessments of the heroes might be better than mine. I'm just doing this for fun. Maybe there'd be some good discussion and will help me improve how I use or look at many heroes.
My use of Black Knight is not extensive enough. To be honest, I don't have a grasp of how his moves and abilities work with each other. I have only used him in PVE and I can only remember doing Bleed and then Hemorrhage. But that's the thing with PVE, you can see your opponents. You'll tend to use him with enemy sets where that simple combo will work (such as a set with non-mechanical blasters) so you won't get to see how else you can use a hero. I'll try him out in PVP one of these days and come back.
T'Challa is great and not that hard to figure out. He can work well alone. Make your opponent bleed, get some Panther Stance going, and exploit those bleeds. With a Blaster in the opposition, he can get going very fast. Team him up with Cable, or an agent with Extra turn gears, and he can get to Pawnage mode quickly, even in the absence of enemy blasters. In the days where the methods for removing buffs and debuffs were uncommon (if not rare), I used him in PVP. He can still be viable today, but with all the scrolls and Rescues in the scene, he'd be slow. He's still powerful, but he'd just require you to think way more on building his teammates unlike before.
His moves and abilities capture his leadership and protection qualities pretty well. His passive Inspiring Leadership raises the team's stats, and he is centered around protection, so that his team can do their thing with relative ease (way way easier before, when attacks that bypass protection are not as numerous).
Cap A has been a contender for the title of Best Tank, especially when equipped with his WW2 uniform. I personally give him this title. That's because (under the presumption of WW2 equipped) he can go on the offensive while protecting his team. Bonus is that he counters with a well-damaging move. Damage really piles up. A pretty good fit with his tactical abilities depicted in the comics and other media.
He's not a big puzzle. He can be a heavy hitter with his L2-L6 combo. Pack him with Attack and Accuracy and he can bring the pain. However, in many situations, the Stun turns into Recovering before his next turn comes up so he won't be able to exploit it. If there's a Blaster in the opposition, then you can take it out quickly. In the absence of Blasters, extra turns would be your friend.
But even if you don't manage to hit with heavy damage with the combo, Constrictor still has nice utility. His L1 puts Generalized - a debuff that is always welcome in my book.
Plus, it's pretty entertaining when you get to call Magneto. I hope he'll be changed in the future so that his Distress Call can also call other characters.
Cyclops was pretty lame before his revamp, even with the P5 alt. Well, that's all in the past now. For me, he's now one of the strongest heroes - maybe the best usability-to-price ratio out there.
Stats Good health, kinda needs more SP (not an issue in PVP).
Midway attack means it would be easy enough to build to outstanding proportions. Midway defense would also be easy to build if you want to. Above average accuracy is desirable since you'll want to build it because of his deadly crits. Low evasion appears as a con, but nowadays you're better off relying on abilities for evasion rather than the evasion stat (especially in PVP). So, I don't think I have a problem with that.
Optic Blast is amazing. It has a pretty nice damage. Plus, Flanked is a nice debuff. You get SP efficiency with follow-up attacks.
Exploit Weakness is one of my favorite attacks now. Disadvantage is amazing. Mostly, it takes a good part of the class bonuses out. The best is when you put Neutralized on an opponent Bruiser. That's because Neutralized doesn't only take away the whole Bruiser bonus. It goes beyond that by preventing any other stat-increasing buffs (most notably Cap B's Roar of Avalon and these +25% buffs).
Evasive Maneuvers is one nice utility move. Who doesn't love Quick Action? Raising the team's evasion might be negligible (especially in PVP and higher end PVE), but giving your whole team counters? Now that's awesome. Yeah, yeah, there are a lot of uncounterable moves now, but it still works lots of times. Best case scenario is the opponent uses a non-stealthy AoE. Gives your team an edge - accelerating chargers (Thor and his MoM, Gambit and his Kinetic Charges, Finest Hour peeps, Magik with her Soul Charges, and the like), speeding up debuff setups (Iron Fist puts Combo setup, Cap B puts 2 red boxes, Pressure Points peeps, and the like), and just plain damaging your opponent. Of course, coordinated attack (and similar effects) procs are still better since they rely on your active aggression but one cannot ignore this potential.
Mega-Optic Blast is something I rarely use. The first three abilities are enough almost always. I use this just to see it but that doesn't mean it has no functional purpose. Incapacitated is one of the wonderful debuffs. You can also finish off some red zoned enemies while doing some damage on the other opponents - heavily damaging on crits (Targeted, his own Phoenix Potential, or any sure-crit mechanism you have).
Natural Leader felt pretty meh when I first saw it, but after it was fixed, it procs a lot. Those stat-boosts can save your life at times.
Phoenix Potential: Flames of Destruction is simple. It's a way to get Blaster bonus without being a Blaster, etc. It really doesn't do anything more but that's all it needs. Sure crits and penetrating defense? Definitely amps up your offense by many levels.
How it All Ties in
Now, Cyclops really feels like the field leader that he is. He increases you team's overall effectiveness - boosting stats, dealing with counter-classes, speeding setups, etc.
He puts weak point with which he benefits from himself (deadly crits on L1 and L9), or sets up a teammate pretty nicely. Flanked is another tool for speeding up offense. You can pick someone and you have the potential to perpetually make that guy Flanked (L1, then L2 next turn; he'll follow up with the L1 so the guy gets Flanked again). If you give Cyke enough health and defense, he can survive long enough to accelerate your offense and deal significant damage himself. He's really impressive, especially when you remember that he costs 15 CP, 50-60 or so if you count the P5 uniform. I got the Tac P5 during the Phoenix Fire Sale, so his total cost for me is 49 CPs.
More discussion in the next update...
Even after all the nerfs and whatnot, the White Queen is still one of the most formidable heroes (especially with the P5 equipped). Don't let anyone tell you otherwise.
She is a good support character with simple but effective offense. No wonder she was overused back then.
To be continued... I plan to make a more comprehensive review for the characters, wherein I analyze each of their moves and abilities. That's definitely gonna take time.