Actually just in general I suggest taking 3 levels in hexblade for Force of Personality and Mettle. That right there is a pretty much 95% chance to pass any save for no damage, ever, rather than for half. Even on a natural one that's gotta be like +27 will save
Oh shit you get Cha to saves vs spells, so you get +57 plus all kinds of save boosters on will saves, and I think you get +CHA on fort saves as an undead, right? or is it Wisdom? So you've just become immune to anything allowing a save, now that you've got evasion. I'd ditch those last 3 rogue or scout levels for hexblade, then you get evasion, mettle, probably a better hit die, a save boost, and a charisma based curse for minor fear.
I think hexblade might require nongood, though, so you'd need to go paladin of tyranny, but you don't necessarily have to kill everyone (unlike a paladin of slaughter), you just need to have plans working towards their eventual destruction.