Currently everyone starts out with humans. But when you choose to try out the Lich race or Dwarfs, you hafto go throgh the same ranking up, as everyone else, meaning you get alot of heroes that have Humanoid Specific traits, and therefore work better with humanoid armies. Yes you can purchase the undead or dwarf heroes for $59.99 / 99.99 each through the store.
And then you kinda hafto start over with your entire army, because your human soldiers are now worthless with the race change. So you walk around with human heroes, an undead army, and the two dont work together very well.
I would suggest that players get to choose race from the beginning on a new server. Then choose between one of 3 heroes specific for the chosen race. And then have the heroes aquireable through ranking up, being for the specific race.
And then have each hero correspond to a specific hero from the other race, when you change race. Just like with the research and buildings.
OR, change the abilities of heroes to include ANY army type under your control, instead of Avalon's Humanoid only buffs.