My strategy for GUV's: make a mental note about there being a GUV, run like a little bitch, close the chaos gate, and if I feel bored after closing the gate, attempt to clear the GUV. If I get killed in the process, I don't really care anymore, because I know I've already closed the gate and "beaten" the game, everything after that is a bonus.
Edit:
Attempting a greater undead vault at level 25 is like going into the African savannah, running into a troup of lions and - instead of running like a little bitch - attempting to kill them with nothing but your Swiss pocket knife as a weapon.