Vamp isn't an issue, since lifesteal is capped by your damage. At a certain point, every point of DR you gain is a point of lifesteal lost. For vampires that go above 600 CP, there's pretty much zero benefit to be had here. As for level 10 Monk with 5 corrosion, that'd be only 25 health per tile, but you take additional damage from each attack. I'd actually be more concerned about a mid-level Priest than a high-level Monk. I can't recall if corrosion damage is applied before or after resistances; that would certainly change matters.