I don't have any experience with the type of setup you're talking about, but I can say that even in PvP I would dearly miss somebody capable of ressing!

When I started my hunter + druid team, the druid could only res once every... erm... thirty minutes(?) or so, and it was deeply painful doing pretty much anything.

Even now, I frequently lose one of my guys (but VERY rarely all of them) at various points in world PvP / WG / AV, and would hate to end up doing a GY run with the whole team to recover. I doubt soulstones - even with the 15 minute cooldown penciled in for 3.3 - would be enough to stave off the frustration.

So I reckon you'd really miss a healer / resser, regardless of class. I suppose you could always go with 5 sets of jumper cables and hope for the best though....

I'll leave a more in-depth analysis to those who have experience with a Disc Priest healer.