Rank 10-15 4ppl, try the bloodshore bells on the little island.

Rank 15-20 5-6 ppl, Opos in muntuy cellars in the circle rooms

rank 20-28 as CK mentioned Puks in Nanawa mines north of the aetherite this works well for 6+ at rank 20, and 4-5 25-28

rank 29-35 3-4 person group, Dobylns in Copperbell this will get you around 15-16k if no one is soloing them. need to have regiments worked out for diremites though or they can get really nasty and take awhile to kill.

rank 29-38 5-8 Person group Nine Ives Eft camp in Black Shroud

Rank 39-44 4-5 person group at Peiste near camp Riversmeet in Corethas

Rank 45-50 5-6 ppl party, eft camp near Sorrel haven in the Black Shroud

Alot of ppl mess with raptors around the 40s as well but they always seemed to give me less sp over time then the other camps in the 40s.

All these camps should net you well over 15k sp/hr with some getting near 20k if you have the right number of ppl and the level range is correct.