From playing a survival specced brewmaster occasionally?

Ox stance: 20%

Shuffle: 20%

Base mastery: 5%

1% for every 960 mastery rating beyond that point.

At this moment, I calculate that with some gear swaps, I am able to dump roughly 19-20k stats into mastery if I so desired and I'm still a few ilvls away from bis. Plus the 3k from mastery raid buff = 23-24% more mastery, for a total of 68-69%, probably 70% in bis T15. Ok, so I rounded a little, sue me. It'll be ~80% passive in T16.

On top of that, we have 2pT15 which is up roughly 30-50% of the time, which provides another 12% stagger. Fort brew is up ~10-15% of the time for 20% more stagger. Rune of reorigination procs - if you choose to use that trinket - will supply another 10-20% stagger about 25% of the time. Hence the range of stagger I mentioned. If anything, I'm underestimating the amount these procs add to the average stagger value.