I agree with OP it is a useless skill; add it to the list of other useless skills that somebody posted a thread on not too long ago. Maybe, one day RW will take action on that list..... IDK, could happen. While they are at it maybe they could address my M/K's shield of discipline which requires equipping a shield which he is not allowed to wield. (Before anyone goes off on that skill being a Knight skill and...so what, it takes a skill space, fix it)
Anyways,...back on topic. Replace the skill with one in keeping with the combos theme, which is vampiric. For 5 seconds caster is transformed into a bat; increasing movement speed by 15% and allowing casting while in motion.