Impaired people and cries of "OP!"

[Alexei]

Wait, your current party has a Mineral Warrior Warblade and a DMM Cleric, and they think a God wizard is too powerful?

Yes. 
More specifically, a Mineral Warrior Lion Totem barbarian/Warblade who full attacks with whirling frenzy after a charge and owns everything, and a DMM minicodzilla cleric .

For ToH, I already pointed that to them, we'll see, I'm not DMing till september so plenty of time yet, I might even have changes in the group depending on university or real life issues...

[caelic]

Tomb of Horrors is definitely a killer campaign, but it seemed to me like it was full of arbitrary "fuck you"s more than requiring actual tactics.  Don't get me wrong, it will definitely kill your PCs - just be careful not to take it too far - people don't enjoy being mocked when their character dies simply by going through the wrong door.

Reputation aside, ToH was definitely doable if you were willing to think outside the box and use innovative tactics.  (We burned through a LOT of animated undead as PMDs the first time I played it.  Lacking weapons capable of killing the demilich, we pulled a Bag of Holding over him as he started to rise the second time, dashed back to the green devil-face, and threw the bag into the Sphere of Annihilation there.  Good times...)