I have a similar dilemma, having a Naxx geared feral druid on my main account that I'm likely to use for the tank for my 4 shammies rather than push up a DK or dust off the 61 pally on the main account.

It's worth noting that dual spec is made for situations like this, the "should I dedicate a healer or not?" I plan to make all of my shammies dual spec with elemental and resto as the pieces.

Down the road my 4 boomkins will likely also moonlight as trees.