Maybe take a look at Anistuffs' playthrough to see if you can do anything differently. But it certainly is a tough level, especially if you missed the hidden blood magic spells ;)
one thing Anistuff could have optmized in general:
instead of spamming fireball or fire wall to deal 1 damage per turn, he could actually use fire ball/wall only when necessary to make people burn again and use shock instead at close range.
like, if the enemy is burning and you use shock, you make 1,5 hearts damage isntead of the 1 heart when using fire on an already burning enemy :-)