Now, as soon as you teleport in to the Fighter's Challenge, move forward (as well as cast spells or use missiles)... you can either get in front of the gate, or one step from it. You'll want to fight your way to the gate, then to the keyhole to the right of it.
Now, use the gold key at the keyhole, fight your way back to the where the gate opened, and go in. Now, you'll only be fighting enemies in front of you, and it's all easy at this point.
Another trick people have found is to lob grenades in through the entry teleporter to wipe enemies out before they can even touch you.
Yeah I don't like that, you'll lose a bunch of xp.
On a similar note, I started the game over, and there's that early trap where you get ambushed by three skeleton warriors (second level, I think). Kind of funny, I just threw a torch onto the pressure plate from outside the room, it closes the door and launches the ambush... and all you do is open the gate and fight them one at a time.
I agree, that room had methods to abuse. Know which one I hated more? The herder room. No safe spots, and poison cloud spewing until even your fighters die in a pool of their own bodily fluids. They are persistent, unrelenting morons. So I just lobbed a ton of bombs through the teleport. They give crappy xp anyway. And even then they still didn't all die. I had to run through, grab the keys and get out of dodge. With one person left alive. How is this considered fair? I have no idea.