Absorbs 50% of incoming melee damage, to a max of 1600. That means a mob would have to lay out 3200+ in order to drop this in a single hit.
Unfortunately, quite a few mobs can do that.
This spell would be much more useful if the recourse effect stacked with the Cleric's Vie line of melee mitigation buffs. However, since it doesn't...can anyone say whether this will over-ride a Cleric's Aegis/Rallied Aegis of Vie? Or would it not take hold if Aegis/Rallied Aegis was up?
In my (admittedly unprofessional and wholly useless) opinion, I'd much prefer the 10% that Aegis/Rallied Aegis of Vie Rk. II provide (up to 2704 or 2600 total, respectively) and lasting for 60-ish minutes, than 50% (up to 1600 total) for 18 seconds.
(Of course, I'd absolutely take my Veil of Mindshadow 3/3 over all of them; mitigates incoming melee damage by 80%, up to 4500 total, lasting for 54 minutes. And it stacks with the Cleric's Vie line! /mad cackle of glee)