Priest (Holy) + Shaman (Elemental) or Priest (Shadow) + Shaman (Restoration)

I'm now thinking that I'm going to go Shaman as healer (Restoration) and Priest as DPS (Shadow).

My rationale is that the synergy between the Priest and the Warlock is too good to pass up. (My warlock is demonology specced and has been destruction specced before.) Add to that the nice, relatively passive AE healing/mana impact of the Shadow Priest and it seems almost like a no brainer. One downside is ultimately having 3 clothies all vying for DPS armor. A few questions, however:

1. Will a Shadow Priest match an Elemental Shaman in DPS?
2. It seems that a Shaman can be fully effective as primary healer in a 5 person PvE team. Agree/disagree?
3. Thoughts on the trade off of Totem of Wrath for the Shadow Priests offensive boost (primarily to the Warlock) as well as the mana stream/healing stream from the Shadow Priest's talents?

Thanks.

As far as I know pretty sure someone will correct me if I'm wrong :P
that nifty synergy of priest and warlock gonna be gone by next month.

1) sure they do about the same dps if they have about the same level of gear.

2) I agree they make decent healers.

3) shadow priest will be harder to maximize dps but yeh get stam buff , shield and fear which can be nice at times
whereas shammy yeh can drop some extra totems and do a lil aoe damage.
Its a toss up really