Been trying to get PUGs together to run the Shadow Tombs (on normal, advertising for characters level 8-12) for a few weeks now, and having very little success. I'd like to request these be revisited sometime, and the difficulty level looked at. Mostly the respawns are the killers. The quests seem sufficiently challenging for an appropriately leveled group with no respawns at all; maybe it's time to get rid of them, or at least reduce them significantly.
As it is, a typical successful run in my experience has involved hours of battling through one Tomb, with multiple deaths (including the occasional wipe), at the end of which marathon the group falls apart and the process has to be started all over again (usually another day, as even I am sick of it by then) to get the next Tomb done.
I'm not saying everyone has this much difficulty with them, but it would be nice for an average PUG to be able to get through a level 8 quest on normal (not a raid or even raid prereq) without quite such a struggle. In my opinion, getting rid of the respawns should be enough to bring them down from "major headache" to "potentially fun".