I've only done 25 mans this tier, and I have not found a need to gem Stamina, honestly. I have definitely found that quite a few fights mandated at least one Stamina trinket and for the longest time I actively avoided reforging around a Hit/Exp trinket so I was able to sub in two of them when necessary, like progression on 25H Horridon or tanking the bats on 25H Tortos. (It wasn't until fairly recently that I felt comfortable doing either of those fights without a Stam trinket at all, maybe I'm just overly cautious though :-P )
Gemming Stamina? I really have never found that to be a great idea. I've even had horrible horrible luck with a Soul Barrier (never dropped.... soooo many Lei Shen kills, all but one on 25, and not a single drop - and a lot of coin fails to boot), so I've had to compare Spark of Zandalar
versus Relic of Niuzao
and it still makes more sense to swap the trinkets than it does to swap gems. I was basically trading Haste to Stam at a 1:1 ratio (versus gems being 320 Haste versus 240 Stam). The difference between the on-use and the proc is actually not that big of a deal either, Strength is better than Dodge by a fair margin but neither is that stellar, and on-uses are much better than random procs. I really don't care too much about avoidance procs/effects either, tbh.
That's just kind of an example, but my point is that high Haste really works out to be a huge survival gain even if you're getting hit with quite a bit of burst damage. Shield of the Righteous uptime is the main reason, but you also need to consider that because Sacred Shield and Seal of Insight scale so ridiculously well with both Vengeance and Haste, Haste is just an all-around damage smoothing/reduction stat. The only thing it doesn't do is increase our maximum health, which does matter for some mechanics or fights that truly challenge your health pool.
Aside from awful gems, you should swap out Colossus for an enchant that does something useful with ToT levels of damage. Dancing Steel and Windsong are both good, I've used Dancing Steel thus far but I'm testing the theory that Windsong performs better in a lot of the 25H fights where you have really damn high Vengeance. (I doubt it's a big deal either way, both are solid.)
Uhhhh what else. Be neurotic about swapping around some talents, I'm constantly fiddling with my level 15, 60, 75, and 90 talents.