The Escape From Durnholde

They removed the attunement quest in patch 4.0.3

Just a tip, you need to complete this quest ( http://www.wowhead.com/?quest=10277 ) to be able to queue in for this instance with the random dungeon queue.
Unfortunately nowadays people are too lazy to actually go to the Caverns of Time and do this quest.. so none of the Caverns of Time Instances are actually used.

If anyone loses Thrall during this, try looking for him at 52,41.

at some point in the road, after you cross a bridge (there should be a rare turtle to your left, friendly), Thrall will step off the road and go along the river up to Tarren Mill, and stop behind the hill that's next to the farm, so that he can infiltrate the city without being found out.

You'll have to speak to him again there before you proceed.

Hope this helps and solves the problem of " where did Thrall go? I lost him!" =)