Just going to add a quick note. I’ll properly look through it when I have the time (and re-read, my brain takes a while to process written information).
I feel you on the mythic Nyth, I feel pretty useless myself on that fight. And I like Ursoc too, such a wonderful fight for a resto shaman I feel, plus those CBT timings makes you feel semi-godly 😀
The logic is that you go crit for chain heal so you won’t oom as fast (since chain healing is taxing on the mana) and a single target build won’t oom you as fast as you’ve noticed and thus mastery is generally more benefical for progress. Gear is also such that you can’t really decide what you get given so a lot of the time you’re just at the mercy of rng. Also some fights you’re just not going to chain heal as much due to the nature of the fights, no matter your build or stat usage. Have you tried using Wellspring on the fights you’re finding yourself high on mana? I’ve not ran with it myself (almost only run with high tide). You could also trying using unleash life with chain heal and high tide for those burst phases if you can and see how that works out. It’s hard to say why your raid is dying to burst damage, that could be because raid cd’s aren’t being used effectively or the other healers aren’t preparing for it. I’ve not found a use for ascendance in raids myself yet (although not that far into mythics so this might change) but that could well just be a comp thing in all honesty (I often run with a second a resto shaman speced into ascendance).
The thing with mana as well might just be because you’re running more healers than needed.
I’ll look into the video, some more logs and re-read and think. This was just what came at me at the moment. Right now, lunch time!