I think the best solution I've heard for Clemency is to change it to a super long duration HoT.

First, it helps PLD's aggro issues. You cast it on yourself and maybe 1~2 other people before the pull and the initial aggro feed from the HoT would help PLDs solidify early aggro.

Second, it fixes the tendency to over heal. A portion of it will still over heal but it won't be as hit or miss. Being a HoT will also make it easier for healers to gauge how they should adjust their own healing around Clemency.

Third, from a design PoV, it helps differentiate PLD healing from WAR's Equilibrium. Rather than just being another huge heal, it gives PLDs unique healing utility from the tank role.