Most decked undeads don't put them in situations where they will die to a single opponent, no matter the build.
I like marans with landslide, separate them from the army and eyes to prevent sleep. Knowing what they are resisting is helpful too, since most mummie cover the holy and fire vulns, and far as I know PC undeads are not actually vuln silver like some NPC ones are.

I played bards and they did not give me much trouble, but my only way to kill them was a strong fiend, since they could not be rescued from it, and they can not escape it. If they don't have a resit mental prep handy fiends can ruin an undeads day since they are immune to most undead spells as well. Not sure if this is really viable though, fiends are not what they once were and most undeads are smart enough to not be caught by them.