That was a really tough fight. I just finished it today as a lvl 34 mage. After getting killed multiple times with two blows, I came up with this strategy as a mage: RUN!!! :P
I quickly jumped away, ran around the columns and casted a level 10 demon and a necro pet. My buddies made all of the enemies focus on them in the inner part of the room. Then I jumped right in the midst of the enemies while they were occupied and cast a level 13 firewall and repeatedly did a level 6 whirlwind. It took a few times.
