Those blinking warlocks were an unexpected display of bravery, I'll give you that
. Well, you did kill 17 ghouls, sieged a fort and horror marked my baron, that's something. I'll have to send new troops now and break that seige, which will slow down my building of a vampire defence by two turns at least. Outrageous.
About those offensive blood spells, could it be they don't work on undead, and that's why your mages go off script? Inexplicable mage behavior is usually tied to targeting issues of some sort or the other.
Blink should probably be removed from the game or given a gem cost, I don't see it causing anything but trouble and frustration. If you want a blinking commander/mage you can just forge sandals. And that's not very often, blinking assassins with magic bows are funny though.
Interesting thing there, that we could see in this battle, a master casting blink also blinks all the slaves. That can actually be useful in a linebacker communion storming a fort, I've used it that way, but that's extremely niche though.