Well, since mesmers have a number of skills that steal skills (Inspired Hex, Inspired Enchantment, Arcane Thievery, Arcane Mimicry), I made a themed "mimic" type of mesmer. I just noticed when I used him, though, that the stolen skills suck. Unless you have a matching secondary with properly distributed attribute points, any skill you steal will be at level 0. The Fireball I stole from a Hydra outside Augury Rock only does 7 damage! This seems like a very problematic bug--or, at the least, a game mechanic oversight.
EDIT: A screenshot of said problem: