I've always assumed, for dungeons it would be 1x Bear, 1x Resto, 3x DPS.
With a choice of Cat DPS (using overlap PvE/PvP gear) or Moonkin DPS (with a second set of gear, but not in melee range).

Four non-finisher moves, will result in an instant cast Nature spell (with any finishing move), more than 95% of the time.
And every melee crit, restores mana.
So your cat DPS will likely never be short on the mana, if you only rely on the Predatory Strikes heal.
But they'll oom fairly quickly, if they have to chain cast heals.

I would suspect, initially they might keep up on heals for some normal dungeons.
And well down the road, when we overgear heroics be able to heal those too.