Shifting needs to run them out of mana as it did season 1-4, as it did pre 3.08. Shifting non stop, no need for innervate, most likely not even aware ferals have innervate, but who can blame them having a full mana bar.
And yes resetting GCD is all it does, that and your 1.0 attack speed. Unless there's some feral w.o lolol 5 points furor lolol. Pretty good trade off.
Ferals have an entire 6000 mana before MotW. If they're "shifting out to cyclone and heal" all the time, they'll be oom in no time. It's only shifting that is cheap.
In BC, in PvP gear, I had 9200 mana with MotW and shifts cost 580 mana.
In LK, in PvP gear (or any gear), I have 6600 mana with MotW and shifts cost 244 mana. At the same time, CC and healing have almost doubled in cost.
So I can shift more, but I still get much less out of my mana pool.
Of course, my regen is better now because of iLotP as long as I am actively attacking something. At the same time, I have about half as much actual MP5 as I did at 70, and this will be cut another 40% next patch. I get about 1000 mana, total, back from Innervate or something dumb like that.
Spamming hibernate/roots/cyclone at a feral is an extremely effective way of controlling them significantly (you trade a 1.5s cast for a GCD. Stack hots, do that, and they aren't doing any damage if they're on your partner). Hibernate being instant cast would give you TWO spammable ranged CCs on ferals that do not share DR and that would be completely unavoidable (you ALREADY have two spammable ranged CCs to use on me, but at least I can avoid one of them). You think that wouldn't be ridiculous?