No reason not to have Radiant Servant and even w/out the PrE empower healing is a must for a healbot cleric. It is more mana efficient for heals that empower or maximize spell. As many have said already, Radiant Servant gives you an AoE burst heal and also a regen aura. You use turn undead for it and not SP so with your high CHA you will get a fairly good amount and they also come back w/ time. Radiant Servant II acually makes the bonus to healing spells from empower healing 75% instead of 50% at the same cost. I'd say altogether that would save a considerable amount of SP which you can then blow on whatever the heck you want.