Like others have said here, haste and mastery are very close together in priority. Ignore the ones saying mastery is better, ignore the one's saying haste is better. The key thing is haste>mastery, until YOU have enough haste to heal how YOU want to heal. Personally I don't want large amounts of haste so i prefer mastery over it. Chimeron is the only fight i find myself thinking "maybe i'd like more haste" All other times, cho'galls shadow nova, Nefs crackle i always have enough time to heal up from perhaps as we move into heroics now i'll favour haste more but for now i prefer mastery, but it's not a case of mastery is better, it's what works for you, 12.5% raid buffed isn't a "magic number" but it is the point you get another renew tick which after the patch will be more important but now it's just making a bad spell slightly more acceptable. Crit is bad as everyones said, i do take crit pieces offset for disc to swap in, crit vs haste for disc is another similar discussion so it's no good saying take haste if you're ever going disc either.