This is the best WHM toy ever. Sad to see talks of "Esuna" and SCH's "Accession" stratagem here, when any real mage can tell you they are very different things from "Divine Veil". Accession can be used with a ton of White magic spells for SCH but has a 60sec recast on each stratagem with a max of 4 @ 75. Also doubles the spells MP cost, cast time and recast. "Esuna" is for more light events where the mage can be near the party he is in. Great for things that spam more than one spell. But mixing this with "Sacrifice", switching to and from "Afflatus Solace / Misery" sure to slow you down a bit. But as Houppelande said it does not work with silence or petrified.
For a WHM you really want to be away from your party at all times making "Esuna" kinda a risk at larger events. SCH's "Accession" can not be used all the time and if there stratagems are down, your SOL. "Divine Veil" effect works on any party a spell can be landed on with a normal AoE range from its target.