1) You are now forced to take the underground route to Moonrise tower, leaving an option of the game unexplored.
Or you can simply try hard to pick those dialogue options that would most likely let you live ...
There is plenty of them, actualy the combat itself is quite rare, unless you get exceptionaly bad rolls.

Also, who say that you would let part of the game unexplored?
Its quite possible that the same spot will be accesible from other side aswell.

2) Isn't it funny that Lae'zel would stick to the party even though it must sooner or later become clear to her that we have no intention of seeking out the githyanki? Story wise that certainly is odd.
As far as i know, once you reach Githyanki patrol, Lae'zel leave your party and join them ...
Unless you have her in your camp, in wich case its just as funny as it is when you kill them all, and simply dont talk about it with her.

3) The designers work on the encounter is a waste, because we all get the hint and leave them alone.
Nah, you just return once you get stronger.

Bcs no matter how many hints are there ... players allways want to see things.
