I enjoy the idea of having massive scale wars, although it does seem to slow down on the web version (I assume downloaded would run better).
Enemy variety is lacking, since there's only 1 enemy type so far.
Some characters I would love to see would be snipers that have insane range, perhaps even having piercing attacks.
Mages that do nasty AOE damage would be good.
Necromancers that summon skeletons would be fun, and gives reason to use the back part of the map.
