I found a place in the Valley of the Fallen Heros in Icecrown where Fallen hero’s Spirit – yellow mobs run past you , and you can pick one off at time, – or as many as you want. They keep comming in a constant stream.
Depending on how many ran past in a group I would dot one, then another, and if I got more then three would use Mind sear. if I took on Six of them I would sometimes have issues, but because they don’t instantly agro you ( as they are yellows) you can take on what ever load you feel comfortable with.
Fallen hero’s spirits seem to have a decent cloth drop table, Thott says 30% drop rate. I also got a Level 73 blue off one, and a smattering of greys and whites and greens.
Its a matter of placement, there is a section in the corridor where the Spirits run past - I camped out the spot just before where they get converted to a Converted Hero – and the mobs are red.
Edit: I’m going to justify some reasons why this is a good place – these reasons may not apply to everyone /class
All the mobs are melee - No trying to get casters in to AOE range.
Its easy to get them in group to Aoe.
All the mobs are yellow – and will only agro if you are agressive to them. This makes it easier to pick off how many you want.
They don’t hit hard = 200-5oo on cloth
They don’t ever run out – you can stand in the same spot for hours and they will keep running past you at intervals – in singles – in groups
They aren’t required for a quest _ ( or if they are no one else has been killing them ) so your not competing/depriving people of mobs needed. Means less competition for the kills and an easier farm