Best to have at least slayundead 3 and WoT if u plan to solo these. Camp a willsapper or the like .. (slow proc weapon) to help lower their dps. (I can easy solo these with su2, but I am on FV. willsapper was in bazaar, as was the qvic armor I'm wearing..) Otherwise it's faster at 70 to kill in the 50 hotzone for aa's.
They do drop power of ro a fair bit tho.. worth it if you don't want to pay the 200-500p per tag on them.
This camp with "a fallen spirit" and "a fallen champion" is pure expe for grownup palies. Mobs have aprox. 35k and hit max 700 mostly less than 200 with WoT running and hot-potions I can spend my mana on nuking. 8% AAxpe on lvl 70 killspeed raidbuffed with epic 2.0 15 to 20 per hour - on lucky slays up to 30 - fastest was 3 rounds with 3 slays 12+k
Was using the 67 Bard Fear Song which works up to level 65. I was able to fear some of these, but not most. So I would say level is 65-69 being mostly 65+.
Soloable by druid 67. Just snare pull, Root and dot them up. They do have a nasty snare of their own so make sure you are far enough away to reapply root when it breaks. Very easy with Druid/Ranger Duo.