Originally Posted by MythMage
Even if it stacks with no other natural armor at all, +8 is extraordinarily high for a PC's natural armor. +6 is really the highest that should ever go, if you're being generous.
I still disagree with leaving the regeneration constant, but it's not so bad on a villain who is expected not to need balancing for PC encounter-oriented play.
The highest I've ever seen was +9, Kyton tainted PrC, 10th level, but that could be taken as early as 2nd level. I'll lower it to +6 if you like though.
What if the regeneration was active only when in that rage-like ability from Willing Possession?