Optimal, don't forget that vampires are also raised through necromancy. Life creatures' Crusaders are only resurrected after a battle thanks to the Life skill. And Life doesn't have the extra growth, like necromancy or summoning, that Nature has. So, it's not 3 vampires, but more – much more! And the Crusaders are doomed.
Added after 52 seconds
to Alex Ghost and OptiMAL
You're both fixated on one of the "favorite units" indicators and trying to prove something to each other!
But you're not considering one of the sides... even all the indicators together won't give you a real result. The balance exists because it's much deeper and more complex than we think.