Another possibility is that you group E and D into a two man group and tag all the mobs with them, you use the others of about the same level to help kill but they dont tag. E/D tag and get all the exp (at the 3X raf) (not sure what happenes if you use a 70 to help kills mobs but there migth be some or a lot of exp lost, so stick with the priests on a/b/c). So you have 5 firepower "pling" the 2 at the end of the raf chain. As E/D get levels they grant back up the chain, although E probably won't be able to grant to D cept one time. Still D is going to level very very fast, and grant to C which then grants to B who grants to A (you get grants from granted levels).

Not perfect but somewhat effective.