Concerning the poll, I said yes. Superman, Batman, Green Lantern and Wonder Woman have so many great tools that I would not be surprised if WB directed NRS to make those particular characters strong for marketing purposes. I have no evidence besides the game itself, so I don't believe it to be a fact, but it is rather suspicious. Most of the dlc characters seem to follow this marketing trick too.
The longer I play the game though, the more I realise that the balance is actually really good. I hated fighting supermans online, but now that I have learnt his weaknesses, I rather enjoy the challenge. I prefer to fight a superman at the moment than have to deal with batman and his trait. A decent patch could bring the cast closer together and make this game one of NRS's most balanced games to date. Unfortunately some characters have weak tools and no amount of tweaking will get them into the top tier without giving them new specials, normals or combos, which won't happen IMO.