1. Why are the alternate vampires marked with a question mark? Do you not like the Stun ability?
2. Why change the alternate Death Knights (melee units) into ranged spellcasters (Plague)?
3. Light Dragons: the only difference in abilities is immunity to mind control/purification, meaning there is practically no difference.
4. Alternate Beasts: I assume a calculator was used? In combination with Return, the retaliate ability is much more important than for other units (the effect of ranged attack), and 3 HP is not enough here (immunity to curse can generally be ignored as it's insignificant).
5. Alternate Witches: why duplicate the overpowered Seduction ability from the alternate Succubus and give them ranged attack?
6. Manticore: is this a glitch with the Stun ability? In WGE, Manticores with Stun don't glitch; however, they don't have Poison (to avoid duplicating the Wyvern).
7. Faceless: you compared mind control with invisibility; here, it's similar to Seduction – players will always choose controllers. What do you think will happen when you combine mind control from the Faceless, mind control from the hero, and Seduction from the Witches?