All three spells here are offensive.
Bloodlust is rarely used.
It can produce the ultimate strength army for a moment,
but it requires a lot of housekeeping due to requiring many shots (being a of a timed duration).
A vampire is a very cheap troop, extremely versatile and an excellent
subversion is the spell of choice here.
Even when things seem hopeless,
you can subvert a creature which suits your tactics, or already has good tactical positioning,
and get back into the game.
Subversion is one the most enemy-annoying moves available
- neither vampire nor bloodlust can reproduce the same level of howling from your human opponent...