I was reasonably beast in Quake III on my old computer, played a buttload of all three Halos on my friend's Xbox, both Star Wars Battlefronts, HL2 Deathmatch, a few CS:S matches, and, of course, Left 4 Dead. I suppose I'm not that used to classes; I'm used to weapons-balancing, not class-balancing. Still, It was hard to find an all-around "general" class (which I suppose was entirely intentional); the closest is Pyro, and he's the also the closest I've gotten to having an enjoyable time in TF2.
I'm guessing the source of my frustration is that it's such a likeable game full of personality, that I want to like it, but can't. Oh well.