I only play resto in raids at the moment but the nr.1 way to find out what stats you should go for is by using simcraft, just plugin your character in and test it out. If you just follow a guide you generally be okay but if you want to optimize use simcraft to find the best results suited for your char.
I've been reading random posts about mastery and the potential it can be stacked to before we are capped; a few people have mentioned around the 56/57% before it basically becomes redundant.
What I want to know is; where are people getting this figure from? Is it correct? Should we be still stacking mastery after this point or is a waste of stats that can be better spent on haste or crit?
Thanks in advance.
without full quote of your source it is hard tell what the context was. at beginning of ptr there was a trinket that added 80% of your mastery to your mastery. with 56% you would have had >100%. that is the maximum. not sure if you referencing to this discussions.
usually mastery scales till you get 100%. so there is no cap till then.
if haste scales better you can look up in simcraft. there is a synergy between them.
with current equip haste usually is better then mastery however due cleave fights etc. where mastery is strong you can also stack mastery and get good numbers from. haste is stronger on single target where mastery is good when you use your cl very often. some people play with 40%+ haste, some play with 60-70% mastery.
personally I picked the way between both see this for details http://www.totemspot.com/vb/entry.php?b=95
all three "ways" are working very good and deliver decent numbers.
tltr: mastery cap is 100%. if it makes sense to push more in mastery or in another stat, this is where simc can help you.