Trigger question, unburrow and attack?

Hi, for a map I'm making, I want to have a bunch of burrowed crypt fiends unburrow and attack when the player passes a certain point. the first part's easy, the trigger condition...just do when a hero enters the area...i just dont know what to do for actions to make the fiends unburrow and then attack.

Ok, I've puzzled it out to an extent...but it's not working. The trigger works except for the first action...the unburrow one. if I remove it and place unburrowed units there, they all nicely attack. What's wrong? Not only do they not attack, but the 'burrowed crypt fiend's i placed there don't unburrow either.

Untitled Trigger 001
Events
Unit - A unit enters Region 000 <gen>
Conditions
((Triggering unit) is A Hero) Equal to True
Actions
Unit Group - Order (Units in Region 001 <gen>) to Undead Crypt Fiend - Unburrow
Unit Group - Order (Units in Region 001 <gen>) to Attack-Move To (Center of Region 000 <gen>)

Ok...I fixed the problem, i needed to pre-research burrowing for the enemy...now I have ONE problem left. This is one of those 'hero with small group' maps, so I can't have well-macroed crypt fiends...how can I tell the enemy AI to NEVER burrow/unburrow of its on volition?