Bladesworn transformation is unusable as it stands, for Paladins, Clerics and Favored Souls alike. Players should want to use it every time the cooldown is up, should the proper moment occur, just like other Faith enhancements. I have literally not used the spell one time in the past month. Think about that.
Solution is simple.
Remove the Healing immunity granted with the buff. The divines would still be silenced and unable to self heal. This (along with the HUGE cooldown and inability to reset with shrines) is a monstrous enough of a penalty.