Quidam said:Then how about subtracting a target's turn resistance from the dice rolled when turning and allowing an evil cleric, by bolstering, to replace the undead's current turn resistance with the cleric's level? This would allow two opposing, equal level clerics to cancel each other out.
I just don't like the idea that there's no way for a high-level cleric to protect his low-level undead from instant dustage the next time a good cleric comes by.
Actually, there are several ways.
For one thing, the radius is only 30 feet.
Keep your undead somewhat apart, force the good cleric to use up turn attempts for each small group.
Secondly, the variant rule does not change the fact that you need line of effect.
Finally, I like your earlier suggestion of adding the hit points. Bolstering only lasts 10 rounds anyway, so adding temporary hit points is no big deal.
I would make it D6 / level of the Cleric, maximum HD of the undead. So, you can only boost a normal human Skeleton D6 hit points anyway.