I suppose the first pip is worth it in the late game as a boss-killing tool then, particularly for the end boss. And it sounds like Killing Strikes would let you snipe low-%hp enemies with the bow? For the most part I wouldn't be willing to put in that effort.
Dominate is the big one.
I felt like the skill that freezes enemies in a block of ice also refuses to trigger on bosses. I had a fight with an Enchanter against the octopus (with the tentacles) where only my Discord and Confuse skill did anything at all, I had to blow a lot of resources on that fight. Though I can't remember what spells I had precisely, and it's possible I misunderstood other game mechanics.