Not sure I'm understanding the way this is calculated...
Shadow Veil is 25% incorporeal. Displace is 50% concealment.
While Displacement doesn't stack with other concealment bonuses such as Blur or Dusk (http://ddowiki.com/page/Displacement), it does stack with Incorporeal. Or at least I greatly assume it does or nobody would even bother with it.
How then is this calculated?
(1-.5)*(1-.25)=37% chance to hit (63% miss).
or is it (more simply):
100% chance to hit - 50% miss - 25% miss = 25% chance to hit (75% miss).
I assume it is the second one. But I know heal amp works multiplicatively so this may too...
NOTE from Soulfurnace! Take into account the 5% miss chance from AC that everyone has because of mobs missing on a 1.
And thanks to Krelar, FuzzyDuck81, and Soulfurnace for telling me it's the first one!
New equation for Displacement, Shadow Veil, and no AC:
(1-.05)*(1-.5)*(1-.25)=35% chance to hit (65% miss).