Blizzard should ban every guild that's exploited this for a period of 1 month, whether it's Paragon or the most casual of guilds. They won't, because that would impact revenues too severely.
They always conveniently leave loopholes like this in the first week, let the elite guilds take full advantage of it, then they block it for the regular players.
Depending on the scope of it, there might not be much Blizzard can do. They'd have to investigate each guild and then identify if they were actually cheesing it or if the data they were using to get that far just made it look like it. At worst, they'd remove the loot and issue probably something like a 48 hour ban. I really only see them hotfixing it though.
Either way, I've discouraged people who brought it up in my guild from doing that. There are legitimate ways to make sure the people you want to get gear will get it, namely running the content multiple times with alts and mains mixed together. Paragon itself gains little from this in that most of them aren't even using the 384 gear. It's an effective way of gearing up alts, but other than that, most of the gear won't be equipped. The only issue with it is that they're able to run the content over and over again, and if five people were missing the same item, they could get all five people their item.
Edit- now that I think about it, they might also just be holding onto the items to fill in the blanks when they have enough T13 gear, so then they upgrade from one 4pc to another.