It's not actually as bad as it looks. The increased healing only applies to the Servant's Healing Domain spells, not other cure spells and such he may cast, so it's less effective than it seems at first. The divine health ability is for the most part negligible to someone who we know already gets remove disease. And the d6 hit die means that at least she's giving something up.
It's a powerful prestige class, but not so much so that I've felt the need to tinker. If I were going to, I probably confine myself to moving the extra Greater Turning a bit later and having 8th level (which grants the Positive Energy Burst and bonuses to everything but Reflex saves) not grant +1 spellcaster level.
If I were going to tinker even more than that, I'd cut the third domain, in which case I'd choose that level as the one to move the extra Greater Turning to.