Yeah. Dispell will clear the DOT from whoever you cast it on.

I beat the beast last night and only had time to take vodal on once. He didn't kill me, those damn fire balls killed me.

As far as the auto cast shield goes:
I created a mapped key which has 4 steps. Each step targets a different toon and casts the shield.
I checked the boxes to not proceed to the next step for 7.5 seconds.
You don't need to check the only activate once box, but you can if you want to.

I put that mapped key into my DPS spam mapped key so everytime I press space bar, the sorc tries to cast shield on each of my toons in order. B/c it doesn't advance for 7.5 seconds, it will complete the cycle every 30 seconds.

I only use this when the boss puts out a bunch of AOE damage.