My only real problem with Carve and Spit is that it is almost never in your best interest to use the MP restore. Using DA + CAS is a +350 potency gain - that's worth almost 3 DAs of bonus damage for Soul Eater.

Conversely, the mana restore is only worth 50% of a single DA. The only time it should ever be used for the MP restore is in a dire emergency (i.e. you don't have enough MP to turn on Grit, or you will drop Darkside if you don't) which you should have planned better for in the first place.