This has been a problem all expansion. Was happening for about 2 hours yesterday and happened again this morning from around 8am til noon. And now it's back.
The community needs to be more vocal about this because it's a huge problem and it is something that is on Blizzard's end regardless of their refusal to take responsibility, it's not like they are powerless to stop ddosing. Blizz also hasn't done a single thing to reimburse players that have been negatively effect by this. Why exactly can't they just make it so that keystone's don't deplete until you complete the dungeon the first time? There's like literally no downside to that, it's not like you get any extra loot, just protection from this type of bullshit where your whole party get's dc'd and the occasional turd you pug that purposefully ruins your runs.