He's not even the best hero. I spent $300 to get him, and regret it. He sucks in the arena, I don't even use him.
I would have to agree with deathfrost13.
The Spirit Mage can float over walls (may pose a problem if he gets too far ahead), has I believe the 2nd highest dps of any hero, and his skill is incredibly good in raids as well as arena.
OP is right I put SM in arena lineup and I dont auto win? wtc? It only gives me one of the best DPS thats also ranged and has a special proc that attacks everyone 2-3 times instantly. Underrated fo sho.
I'm going to have a guess and say the main trouble you're having with it is a low skill level.
The skill really is incredible, with every level it increases it adds another target and even more damage. Once you get to 5-6 targets the damage really starts to pile on, not to mention that it can damage every Hero, and the altar, in the arena in one go!
Give us an idea of how you use your SM and what level's it has and I'm sure we'll be able to turn your opinion around.