Eastern Wastes
 

Chief Ry'Gorr and Elite Guards aggro through the ceiling.

Ry'Gorr Messenger is walking, should be running.

Tain Hammerfrost stays standing, should fall down in the snow while emoting and lay there for a while, get up, repeat.

+1, the guards upstairs warp through the floor from above as soon as you enter the Chief's room.

This belongs in pathing.

He should aggro through the ceiling. Such as other outdoor zones, npcs should not require LOS for aggro. He shouldn't warp through the floor though, he should follow the ramp down.

Looking into this. I believe a recent change affected npcs set to run.
I see this working properly.

Tain Hammerfrost also didn't despawn when giving him "Frozen Elixir".

Should he? He's currently set up for a 10 minute despawn once the giants spawn.

That sounds about right too.

He should despawn into a different version of Tain, otherwise it opens up a way to skip stuff.

Way it currently works:

Ground Tain that lies there moaning, waiting for someone to help. If you choose to help him, he depops, and respawns as the quest Tain.

Quest Tain starts the giants, and a depop timer for 10 minutes. Currently he stands there for the 10 minute interval until depop, or is killed by the giants if not helped.

Ground Tain respawns in 3 hours.

If this is wrong, will need to know specifically how it should work. I can add an instant depop for 2nd Tain upon quest completion, but the guides I read didn't mention it.

This is spot on, except he should despawn when you turn in. You can only do 1 person at a time.