I have impression that I as DM failed to deliver message about this place to you as players. My conclusion comes from Anguis thinking "rock gnomes so paranoid". I'm really worried about this game as I've made it with assumption that your characters - adventures who managed to survive as many battles as to reach lvl 8 - have some tricks to make proper decisions most of the time.
Question
If I would explain you the situation and the clues you see in the tomb - would it help your characters do any better and avoid taking this much damage+spend resources trying to go through the most heavy protected part of the tomb, using brute force.
Suggestion
If any one of you think his character is wise enough and have some gut feeling about this place - I will allow you to roll Wisdom ability check
Quote:
Other Wisdom Checks
The DM might call for a Wisdom check when you try to accomplish tasks like the following:
Get a gut feeling about what course of action to follow