Dragon age origin had some very cool finishing moves for big ennemies like the giants demon and what not . Would be cool if Baldurs gate had a couple of animation like that . One for melee weapon, one for ranged and one for spellcasting maybe? for big enemy like ogres , goblin chief, worg.
Its probably easier to do a custom animation than to do real disembering, as dismembering force you to create a new 3D model for the inside of the creature your disembering. also force you to potentially cut the model into differents part. I'm not sure how its done in mortal kombat but its seems a bit of an hassle.
It depends on the engine, Unity is hell on earth like you said, you need to create a new paperdoll, given its an RPG you have to replicate the paperdoll with the equipment if is not a monster with generic skin. So kudos to Wasteland 3 team working with this engine and implementing gore!
Unreal engine does it in a smoother way its just allows you do cut the paper doll and that it (of course its a shooter engine).
it's great that new engines allow for easier special effect like that. 