I don't know anyone that feels that way about Valla. I'd recommend you play her more. She does INSANE damage. Best AA carry in the game by a large margin, at least until we figure out how good Zul'Jin is. Plus she has good spell damage burst with her Q and W + E auto attack. Not much to complain about with her IMO
And your point that mages do her job better.. Valla is an AD hero first and foremost. Her AA's hit for like 3x what Li-Mings hit for.
Meh, sorry I have to disagree.
Valla is one of the highest skill cap heroes in the game. The pros can play her well because the team can adjust to her very low damage at the start of a fight, and her tiny hit point pool. But outside of pro level play, even at masters and diamond level, Hammer, Zul'Jin and Raynor all have a higher win rate and Tychus is basically at the same level (apologies for triggering Brian!).
I think in theory she's the best, but in practice I don't think we have anyone capable of playing her to the point where she's the best. To be honest, more often than not I prefer something else over her because there are a LOT of bad Valla players who are way too aggressive with her and feed constantly.