Remember how I talked about the DM with the dungeon that was faaarr too challenging?
Nothing but status effects, traps and ridiculous damage for a level 1 character? Apparently he didn't take our advice that it was just a little too difficult. He even compared his dungeon to the likeness of the legendary if not infamous
Tomb of Horrors.
I'm sorry, but there's really obvious differences as to why your dungeon isn't even close.
First off, Tomb of Horrors was designed to be clever and not rules-abusive. It was more trap-oriented than one monster encounter after another. You could find these traps if you were cautious enough and you didn't always have to rule a natural 20 to see them. Its not your typical hack-in-slash dungeon, but that's the point.
On top of this is that the minimum level requirement for the Tomb is 10-14 in the original (Mid-to high paragon in 4e terms) and level 9 for the updated RPGA version. Simply put the characters are given the ability handle whats there if they know what they're doing.
Your dungeon on the other hand is nothing but purposely designed monster encounters that are designed to break the weaker parts of the rules and make it impossible not to lose our group's defender every 3 combat rounds if we're lucky. I mean, dealing with whats left of those kobolds was bad enough, but did you really have to throw Drakes in our rear? Not any drakes though, but Brute drakes. How can we handle something in our flank that has nearly 50 hp and deals more damage the more allies that are next to them? Or how about later on and that ogre with his goblin theif buddy that would use his meat-hook pole-arm to pull our defender out of the way, his goblin buddy sneak-attacking the defender and then using him as a meat shield for our own spells. You even pointed out that AoE wouldn't work because the trapped defender would only take double the damage by the wording of the rules. It's gotten to the point where nobody really wants to play a defender anymore because they're grown to be expendable.
I think a good conclusion is to look at the characters right now. The only person who has gone up a level is the theif, who only survives because he's able to outrun everyone and use the current defender at those times as a scapegoat. Everyone else has died and you can see where each encounter is located by a defender corpse. That's not at all a good sign and your maniacal laugh at each loophole or cheesy combo your monsters make just makes people reluctant to play your "challenging" dungeon. In fact, I think I'm pretty much done playing it.