I've got my 5-man shaman team to level 30 now and can say that once you get them to level 20 they absolutely eat up instances. Before that however they can be hard work. The simple reason is that level 20 introduces a series of talents that makes the shaman life easier (I'm at work now so can't remember them all) but things like lesser healing wave and 5 x healing totems seriously improve survivability (I'm sure the healing totem is at 20 but can't remember!). Ghost wolf is very welcome too!

Anyway, the other advantage is that they are not clothie and can also do decent melee damage so once you let off the initial pull you melee plus shock each mob in turn with the lesser healing on standby (all 5 of my shammies cast this when one is low on health). Not mana efficient but a very quick heal to full health. I've also found that after the pull the mobs generally ping-pong on aggro so you can (if you so wished) set things up to steal aggro from each other and spread the damage.

On the con side I guess taking AOE damage is going to be a problem as will crowd control at later levels. Also controlling the shammies when they are in melee mode takes a little practise to get right, I'm still perfecting the technique but it's coming along. I imagine when they hit outlands I'll need to adopt a technique similar to Xbox where you kite the mobs but at what stage or level I'm not sure. Mana hasn't been a huge issue yet as I can always melee but I would imagine this will raise it's head in the levels to come.

I also find the huge range of spells/totems a bit overwhelming (I thought locks had lots of spells but Shammys seem to surpass them) but most are very situational and I generally find myself using the same spells/totems over and over.

So far I'm really enjoying them (more than my 4xlock 1xpriest team who are also at 30 (I have a 70 lock so probably need a break from locks if I'm honest). I've just got the reincarnation talent which will effectively mean minimal corspe runs on a wipe and I'm really looking forward to chain lightning, chain healing and mail armor in the coming levels.

If you can stick with them until they reach 20 then you'll find them very rewarding to play, I personally was very disappointed with them until that point but now have a big grin on my face as they just seem to survive every situation they come across. At the moment most of my talents are in elemental and enhancement is my secondary tree to mitigate melee damage, I'll probably stick with elemental all the way to 70 but whether I'll need to respec out of enhancement and into resto I'm not sure.