Insane dryads only spawn in specific locations and only if you run near them.

Use a mage and EV the heck out of them. Hiding/Invis is your friend. Presumably, Honor would help you survive those first critical moments at entry. Just wait until the hydra-on-crack is lured to the entrance by a panicked runner.

And if you are having trouble with the dryads, you're going to *love* Saliva's cave...

~M