Hi
I'd like to think I have a pretty good grasp on client side latency in this game, the delay on certain abilities and the buffs/debuffs they apply is down to more than just raw latency tho. The EU data centre move demonstrated that quite nicely and even with sub 30ms latency there's still a substantial delay between the adlo hitting and the galvanise actually taking effect. To give you an idea of the size of that window, early Turn 5 kills required a WHM to be able to consistently land Cure IIs between Death Sentence and Infirmity (the same delay as Adlo/Galvanise) for around 5 minutes at a time. Again, I don't know the exact timing of the delay off the top of my head, but it's in the order of a 1/3rd to 1/2 a second from memory, that's all the numbers you're getting out of me at this hour, hope it's enough.
If you feel I was harsh, so be it. Your example was niche nonsense built upon a pillar of entirely avoidable failures, and the video whilst eye catching, is irrelevant to the game as it stands today (Fun fact, I had so much Spell Speed in 2.4 (Not 3.4, oops!) that assuming I could mash my cure button, PoM was as big a HPS cooldown for me as Divine Seal). SS isn't a feasible bandaid to cover for others mistakes in these cases. Endgame encounters are just too tightly scripted and predictable and in emergency situations such as yours, the better solution is usually with oGCDs such as Lustrate/ED/Tetra.
If I were in your shoes, I'd have put forward something like trying to keep tanks alive when after pulling both gorilla packs and the dogs in Ala Mhigo. That'll get most healers mashing heals on the limiter especially if they didn't see it coming and pocket cooldowns accordingly =(