Finally got around to turning on instant replay in shadowplay so I could capture my issue with PvP, namely Cyro (I don't play IC or BG). Roughly 8/10 of my deaths in Cyro (normally to other players, but in this instance even NPC's!) have been caused by being instantly killed from 5 seconds or more of attacks (going off the abilities etc shown in the death recap) from a single player all hitting me at once, giving me no chance to react.
In this clip something very similar happens, except it's against NPC's and seems to be about 10 seconds worth of damage being held back and all hitting me instantaneously. Notice how I take 0 damage until the server decides i'm already dead. This was today on a half empty Gray Host with the current global AoE Cooldown test active.
https://streamable.com/8wwslv
Considering this is with one of the most drastic of the tests, on a server that was only about half full, surely the current test is already proving useless, this is the exact issue i've always had in Cyro and is still as bad as ever.