I'd be happy enough to keep the shaman ellie as it is generally easier to manage all ranged or all melee dps when boxing IMO. Also your range dps will require a bit less healing further down the track when you are running 85 level stuff.

Your other alternative would be to switch the priest to shadow and have the shaman go heals. I love resto shaman for 5 man dungeon healing and blood tank with earth shield and riptide is almost going to stay alive on his own.

Post your macros for the ele sham and we'll see if we can help out with the dps setup, I can't really imagine why it would be falling behind though at this stage.

Cheers