My style,
The moment I step foot into the area, I use my super-mage, you know... the one with the *wink* *wink* robe, and immediately cast a Planetar next to the enemy. Since the Planetar is immuned to +2 and lower weaponary, she can last long.
So as everybody swarm around her, I use the same mage, and walk right smack into the middle of the swarm, and nobody can see him because of the Staff of Magi.
Invisible, I make him cast Chain Contingency and fill it up with 3 ADHWs, set to trigger when enemy is sighted and to cast at nearest enemy, then I wait.
It is a very good feeling as everybody drops dead from the spell onslaught.