A rest point I am ok with, time extentions in the dungeons current form... I say no. Time is a major factor in the challenge which should not be removed in my opinion. To conquer that objective you need a "no mistakes run" which is very very needed in a game that was 100% mindless zerg with a near 100% success rate before the dungeons.

I would like to see dungeons with multiple fights, and paths where you can extend time. Maby a 45min/1hr dungeon with 2 optional 15 min time extensions to attempt a side goal or something.