I actually agree with this concern. I hadn't heard Cap being Action/Comedy before, that is sad. I also agree TIH had a darker tone (palette, isolation themes, Pyrrhic victory, anti-hero lead, etc) - not as dark as Baleman, but certainly darker than Avengers or Iron Man. That said, TIH was als the least successful of the bunch. The money is in action and laughs. Thor will probably be the darkest this time around, at least in palette, I suspect it will be darker than Avengers, it's that kind of sequel, as opposed to Cap2, which is more
Then again IM3 has some isolationist themes, going back to the cave and all that. It may be too soon to call Phase II derivative, even if Cap will be too light, and imho, the first was a bit too light as well.