As a WHM i never ask for Mage's Ballad AT ALL! Even when I'm spamming Holy in a dungeon, I only ask for Foe's Requiem so we can clear the trash faster. I'll regen up my MP on the way to the next pull or, I'll use the smaller pulls to simply relax and regen mp.

Yes, I tend to use Holy a lot, and that's because it can do 1100 damage on each target it hits on crit. 700-800 on a normal hit. With Foe's Requiem it does even more than that! Most DPS i get the pleasure of being DF'd with are below i95 and aren't pushing the dps I'm doing on large pulls. As long as the WHM isn't begging for Ballad each pull and slowing down the run asking for mp breaks I feel its perfectly fine.