With 35 vampire lords divided into 2 stacks, I could defeat 30 titans without any losses.
P.S. The hero has 60 mana. (Ravenna)
Mass weakening + skull scream + divine strength. The stunning effect worked 3 out of 4 times.
P.P.S. + Skilled Defense.
In general, if the unit is not mechanical or undead, 30 vampires can clear everything that moves on the map without losses. If there are 50 of them, then you don't even have to try hard.