I use Essence of Power majority of the time, as you said, (+) flips on spell damage is pretty hot. Either to achieve the extra flip or offset a low Def variance so I can still cheat. Have to drop that severe damage for 2 blast counters.
Wendigo, in the same boat as it doesn't add much for her. It is another Frozen Heart to bounce spells off of.
Student of Conflict, tried it a few times but you need to manage the Fast as it is an all action. I haven't got my timing down yet so have usually opted for EoP instead for my totem. It is good when you need that extra action, just an issue of getting into a good forward position to benefit a model 3" away. Which may just be fine letting Rasp get in an extra move or spell in.