I don't think that adding a hunter would be worth it. Adding a range dps to that setup would make everything even more complicated than it already is. Also, the hunter and the 2 palys wouldn't have any fear protection whatsoever.
There is also the option to just multibox exclusively warriors and find a seperated healer for the back up. That would probably work best.

After all I think that just like in TBC and Wotlk, the classic 4 ele shami and healer setup will be the best comb in PvP. Holy paly seems mandatory for that setup because of imp concentration aura.
It's interesting that the shami sets have mixed stats of strength and sp. It might be a option to play a ele/enh hybrid build just like 31/20/00. Close by opponents could be killed with a two hander that is imbued with WF and hard to reach opponents with lightning spells.