Roman,
I am one of those that called 'bad DM'. And I stand by that. He had to know that entering that temple meant death, since he knew that puzzle was there. It would be the same if the door magically shut, and 10 ancient red dragons appeared and killed everyone first round.
Tomb of Horrors had a 'doorway' that was a sphere of annihilation, but at least you could detect it a number of ways, and you could successully avoid it, and even if you didn't, it would only kill one (or two).
He may be a great DM in some ways, but a great DM that occasionally TPK's without a chance to avoid it, is still a bad DM in my book. Now, you guys seem to like playing with him, so that is cool. I just think you like playing with a bad DM.
Granted, you guys had the chance to leave after the first few rooms; and so the players are also guilty. But there should have been lots of clues that it wasn't just 'hard', but actually impossible. And with that puzzle, that makes it impossible. Even the 10 red dragons would have been 'easier'.
And I think there is a notable difference between 'coddling' the players so that they can never die, and placing CR 1,000 traps that they can't solve or bypass.