Choosing a class for raiding with low FPS

NSDragon wants to know over on Livejournal: what's the best class to raid with on a low-end system (as in, one that gets only about 3-10 FPS during raid boss fights)? First of all, there's no reason you should be raiding with a system like that anyway -- even a cheap PC will run World of Warcraft better than that, and even if you can't afford a new computer, odds are that you can at least add