Yes, and that's why I hate Crypt Things.
They aren't really all that tough, but they can teleport your characters one by one to go and face Greater Mummies. I just ignore them in fights until everything else is dead. They don't hit hard by comparison, and they won't teleport anybody again unless they lose sight of the party.
If you have a paladin, single-class cleric, or dual class cleric, it should be near or at max level by now. Turn undead can make this area a relative cakewalk. Crypt Things and Revenants seem immune to turning (maybe because they aren't "real" undead), but even Mummies can be destroyed by turning. You're better off hacking down Greater Mummies ASAP instead of trying to turn them.
Revenants do require fire to kill them off. You should have at least one weapon that does some fire damage, otherwise, just use spells. There aren't that many revenants, and you should have tons of spell slots available.
Spectral Guards are a major reason why a character with 100% slashing resistance is such an asset. They can hit just about any AC, so weapon immunity is the best "armor" available against them. Put an immune, shapechanged druid in a doorway, and cast spells and attack in melee (with two-handed weapons) with your other characters.