It's very possible, and even very good for timed runs. My group in timed ZA is shadowpriest + 4 elemental shamans.

We cleared it 3 times in a row now, increasing the time left every reset (last time we had 9 minutes left). The group synergy of 4 shamans and a spriest is so damn insane that i'm outdpsing full t6 mains in a group like that (with only pvp and some badge gear)

edit: full setup:

group1
-------
- protadin
- prot warrior
- holy CoH priest
- Resto Shaman
- Mage (sheeps is handy, thou we might take an enh shammy next time, for the nature debuff)

group 2
---------
- spriest
- 4 ele shammies