Clemency is not that reliable as a full heal and should only be used in tight situations, say the healer is struggling to keep you up or is focusing on other party members, you can pop clemency and heal yourself, I also try to use the skill on a dying healer or try to help top off a dps with the skill, with that said you cannot use it often, you only get 2-3 uses and if you ant to full heal every time you have to spend most of your time riot blade, sheltron and shield bash to keep a healthy supply of mp which will lower your performance big time. Its a very situational ability and I love it.