How does Air Shield work?--2 rquestions

[Epaminondas]

I apologize in advance if this is explained in the manual, as I have yet gotten a copy of the full game, and it's been ages since I've played Dom II.

But my main question is: What do the numerical values you get for Air Shield really mean? Say you have Air Shield of 50. Does this mean you have 50 percent chance of not getting hit? Or does it modify only the damage taken--as in 50 percent reduction? Or does it mean both? Or are my speculations way off, and it's neither?

Another related question is: What kind of optimum Air Shield value should I shoot for in terms of Air Bless? I have played Kailasa and Marveni a lot in the Demo, and I have been using around Air Shield 40. This works okay for Kailasa but not so for Marveni. The problem is that their sacred troops are berserkers, and as soon as they get hit, they break formation and essentially die on solo charges. But if I upped the Air Shield numbers more, then I would lose too many creation points. I don't like the Marveni sacred troops overall, but I suppose that's another discussion altogether...