Spiritshift needs to be buffed a little

The current Spirit**** is not so bad, but I think this needs some adjustment in terms of playthrough. The ability is semi-overpowered while playing in the early of game, but getting worse and worse with passing time. 

Suggestion:

Make this ability a little weaker in aspect of dealing damage, especially at low level. And Give some "progress" for Accuracy, Deflection, duration, etc. In addition, the special ability which can be used while spiritshifting, e.g., Bear's Terrifying Roar should be usable per encounter instead of per rest imo.