Sch should use Adloquium prior to ds whm or off tank should stone skin. You typically don't "have" to use cd's until after the Dive Bomb phase.

I am not saying don't use the cd's during the early phase. I am just stating that your lack of your cool downs should not be whats causing your whm to run out of mana that early.

Ds applies a debuff that causes normal heals to heal for jack squat. Sch should use lustrate after ds to top you back off.

It seem like your whm is over healing and running out of mana. Make sure whm is using Shroud as well. A lot of whm's hang onto it like a golden egg and wont use it.

This is basically a 10-13 min fight and you could get off a decent amount of shrouds in that time. If you have a bard have them use ballad but, in the end I personally think it's the whm's mana usage is the issue.