when you first start heroics it can be brutal.
I tended to have more problems with trash mobs than the bosses myself.
I converted one shaman to resto and this seemed to make a huge difference to me.

I have the DPS butt on as "2" but the resto shaman does nothing for "2" and on button "3" I have the same dps as "2" but the resto shaman has a castsequence staring with earth shield, riptide and a bunch of lesser healing waves on the pally and one or two chain heals in the mix.
I also have panic button that all shaman cast chain heal on themselves with but if I just lightly hit the panic button the non-resto shaman are usually in mid-cast so only the resto does the chain heal on herself. I do this for topping off the team with a mild heal.
So for the second boss in UK I back into a corner and pull to the team and use Magma totems to help burn the trash down.

good luck with that.