Easy way to solve them is to stack barrells along that entrance corridor ...
So you dont block the way in, and yet its impossible for them to avoid it. >:]
You have to be lucky tho, they are resistant to fire damage and sometimes that explosion dont hit them too hard ... other times, i managed to kill one right there, and the other was left with up to 20HP.
I still dont understand why cant we change Race for our hirelings.

Lets us play Githyanki as racist as they trully are!