Have u really tried being enh shammy? I had been enh till 70, ... and spent a few weeks as enh at 70, farming for ele gear in BGs and instances before I respecced.
There is a really a huge difference in killing efficiency when it comes to mobs with some immunities, especially those with LIGHTNING immmunity.
DW enh, SS, WF, maybe add in ES. Mob dead. Need mana? Watershield and Rage. Never had to drink. At that time, I was still in blue and greens.
Now I have purples, .... and yet still find killing a lot more .... tedious =)