I'm running Rappan Athuk. And you betcha that those Orcus-worshiping clerics re-raise the dead in combat. Is this RAW or RAI? Don't care. This is Rappan F'n Athuk, powered by demonic artifacts and--somewhere--deep below, the Avatar of Orcus himself.
Sometimes they just raise up all slashed up and nasty. Sometimes the spell knits them back together (and, heck, with Skeletons isn't that how it HAS to happen?) and often are not knitted from the same corpses. You cleaved that zombie in half? Hah! Here are two half-zombies jumping around on one leg like they are on pogo sticks. You sliced them to shreds, maybe the bones come together, rising out of the putrid flesh and viscera, but are still wet and somewhat covered in carrion, removing their vulnerability to blunt weapons.
Don't want that happening? Well, the party wizard can always use a 6th-level slot for a disintegrate spell. Fireball? Charred zombie. Yum!
A "killed" undead is no longer an undead. It is a corpse. A dead creature. That is until it's animated again.