So far I at least tested it on a Heroic training dummy and didn't seem to miss any of my spells/melee hits, so that was good.
But I just basically went for a balance on dodge/parry to get as much mastery that I could fit in. Was sacrificing dodge/parry to get an increase in mastery for a total of 12.50% shield bonus worth doing? Sorry for sounding naive but what is best way to test this out?
Edit: I did have some parrys, so leads me to believe sacrificing hit/exp for mastery is not a good idea.