It has been said many times that Mastery will have a diminishing return just like Parry and Dodge in MoP, to mainly prevent Tanks from stacking it too high.
After looking at it more closely however, I don't see any sort of DR on it, even after stacking 6K mastery rating.
I still need exactly 272.63 rating points to increase it by 1% (at lvl 90), whether I already have 6K or 0 mastery rating on my gear.
Does this mean Mastery doesn't have any DR, or there's something else going on here ?
I was playing around on a spread sheet with the new mechanics and it's somewhat interesting. I'm not sure if ctc is the best way to look at the new model, and I'm not sure if I may have messed it up somewhere, but from a ctc standpoint the new mechanics work out fairly clear.
If you increase either block % or avoidance by 1% increase to ctc is roughly the same formula
1% increase to block gives [(1-avoidance%)/100] increase to overall ctc
1% increase to avoidance gives [(1-block%)/100] increase to overall ctc
From a ctc standpoint that means that you want to either focus purely on overall avoidance or overall block chance. Haven't really played with actual effects on incoming damage yet though. Once I can find out what the stat conversion rates are I'll likely work on another spreadsheet to give me an idea what to expect this expansion.