[SixOfSpades]

When entering the Temple, you should do what's always the wise thing to do in hostile territory: Have your Thief drink a Potion of Invisibility and go around scouting for Traps, with an Oil of Speed ready in case he happens to attract enemy attention.
Note #1: This place does indeed contain some Traps that *cannot* be Disarmed, something that I detest.
Note #2: Potions of Master Thievery will do absolutely nothing for your Find/Disarm Traps score. Pirengle meant Potions of Perception.

Should somebody happen to engage in conversation with your Invisible Thief, that's all right--as long as you don't actually get *attacked,* that is.

If a Mage happens to Dimension Door out to your party and attack you, do what comes naturally--ask him if he wouldn't mind holding your extra arrows.

Since your Invisible Thief has now scouted out the entire area and knows the location(s) of all visible enemies(s), have your spellcasters go almost out of sight range and cast some Area-Of-Effect spells.

While the spellcasting is going on, your Tank(s) should be drinking every buffing Potion you've got left--what the heck are you saving 'em for?

ATTACK!!!

No Summons Required. In my last game, my PC Tank took Sarevok on one-on-one. I had more than half of my hitpoints left when Sarevok hit the floor.