Well, a team of six wizards, or six druids could probably fare as well as a team of six clerics. I'm just sayin'.

I love the idea, though.
However, bear in mind that not all builds are effective against all things. If they created a team like that one I saw on Gleemax, specializing in massive Fear effects, simple fear-immune enemies pose a challenge.

I'd vary the challenges a lot. It may seem like that 15-headed Cryohydra is a good choice, but when there are six capable attackers all targeting it at once... death ensues.

Also, beware the Sarrukh and the Omnicificer.

Hm... I wonder if the Omnicificer could actually kill Zeus. Interesting thought experiment, right there.