Here's an idea:

 

A party of 5 chanters.  1 of them is a Wild Rhymer (Ranger/Chanter).

 

Everyone sits one screen away from the enemies.

 

The Wild Rhymer sends his pet in first. Pet dies.

 

Here is the key: the pet initiates combat, which means that everyone in the party gets to summon.  

 

Everyone summons like 15 Fire Wurms. 

 

Send the Fire Wurms in.  Once they die, send in another batch.  Etc.  

If you like it and it works, then why not? There is also the "strategy" of throwing lightning bolts and rolling flames from afar and killing enemies without even starting combat.