When wondering about the strength or weakness of a character, my advice would be to hit their forum and check out some of the build guides with a decent amount of posts. Usually every hero has at least one person that knows what they are talking about, having tested many specs/gear builds. For example, Luke Cage, I only have him to 50 for synergy, but one of the more knowledgeable theory crafters named HarryTasker has a guide for him, and a video showing him ripping through Cosmic Terminal Lunar Mandarin in like 40 seconds. Another is Wolverine, he's considered by many to be fairly poor, and while his playstyle is quite boring, I have seen a video of him constantly ripping off crits/brutals in the 200-300k range.
Just like everyone online game, the masses are usually ignorant, and only flock to easy/overpowered classes. My current 3 'main' characters are Loki, Thor and Cyclops, with Loki being the easiest to run Cosmic Terminals with, though his single target damage is somewhat lacking.