Personally speaking, my limit for homebrew are backgrounds, creatures, feats and races. Subclasses are also kind of acceptable, but I'm a bit more iffy on them. I don't really like trying to mess with entirely new classes, though, as they're infinitely more difficult to balance without proper testing. Since the races that already exist are already kind of unbalanced, it's hard to say how strong or weak it needs to be to be "properly balanced."

That said, I am ALWAYS a proponent of stressing the character over the sheet. I suppose it couldn't really hurt to see what the class actually is before dismissing it completely, though?