Chain Heal=/= circle of healing.

I could never run without anything but a priest with my 4 warlocks for this simple reason. COH is instant cast.
Chain heal takes FOREVER to cast in PVP (2.5). Don't get me wrong, Shaman healing will be very good and spirit link looks overpowered, but the majority of Shaman heals have to be cast while standing still. That makes them difficult to multibox as a main healer when on the run.