Resto shaman worth it?

So I'm getting to the point where my toons will be pretty much set in their spec due to gear. With S4 coming on Tuesday, it will be time to buy some upgrades that are not easily replaced. As I sit, I have one shaman who is resto and the other three are elemental. My question is this: Should I keep the one resto and gear him for that, or should I gear him for elemental with the expectation that once my gear is up to par I won't need a resto spec one?

I should mention that I do a mix of PVP and PVE. I'd like to be able to do some heroics, but haven't tried any yet since I still have trouble at times in regular instances. Also, I usually play with my boomkin as my main, but I have a poorly geared pally that is also an option.

Hehe, of course the Boomkin can't tank. Probably about the same level of squishiness as the Shaman, but doesn't put out the same DPS. He's really the weak link of the group DPS wise, but does provide some utility that another Shaman wouldn't.

Do you run one as resto in your setup? I'm considering plugging in my paladin for PVE, but it's such a pain to gear a tank well enough for heroics.