I'm pefectly fine with instances being timed, the way darkhold was done was just poor design since there was no need or reason to kill most any mob besides the bosses.
They could either make mobs in dungeons not leesh (like for example WoW does with trash mobs in instances) and/or have certain parts of dungeon require mobs to defeated to enter (like the gates in strongholds).
Don't be too surprised if the new instances until 2.0 follow the exact Darkhold/totorak formula however.
