Red/green powerful characters are dime a dozen. You got Wolverine 2*, Patch, Thor, Ares, The Punisher, and The Hulk who are all solid characters. I don't believe Ragnarok's nerf is as bad as people say, but the fact that he always only had 2 colors and also only 2 strong color strength means you might as well go with someone who have 3 abilities/colors instead of 2.
Dr. Doom's blue is pretty worthless because blue is the most powerful color in the game right now and it's counterproductive to use blue to feed black. The only case it makes sense is if you've him paired with Black Panther, but even Black Panther has a pretty strong blue even though his black is absolutely broken (still strictly better than Sniper Rifle almost all the time, which is an attack that can normally wipe out an entire team). The thing is that purple/black/yellow are the 'weak' color so having even a marginal ability on those colors is huge. This is also why Magneto classic and OBW are probably the strongest character in the game for their rarity. Besides having completely broken mechanisms, they both have a strong purple ability that is normally one of the weakest color. Likewise Black Panther is probably top 3 overall right now, because he has a very strong (black) and a decent ability (yellow) on the two normally weak colors.