This particular issue was fixed over a month ago internally, but we decided to hold the fix for patch 2.2 rather than hotfix it directly to live.
For those who are curious, the fix is pretty simple. If you intentionally manipulate the mechanics to force the pylons to queue up with nowhere to spawn in unexplored area then you simply lose the pylons instead.
The trick was to explore a bunch of the map but not kill many of the monsters in the area (until it was all mapped). This exploited the dynamic spawning of Pylons in Greater Rifts (Shrines/Pylons in normal Rifts do not work this way) which causes a non-repeating type of Pylon to spawn about every 20-30% cleared. Players could explore a whole area before killing the monsters, which would result in multiple pylons appearing right at the start of the next unmapped area.
It was possible for some very fast moving characters to thus kill up to almost 100%, then enter a new level and immediately find two or three Pylons, loading a player with Pylon power for the Guardian battle. Was… but no more. Had any of you guys actually used this trick and found it successful? Are you glad it’s been fixed?
Note that our recent vote on Pylons in Grifts showed that quite a few players want them removed entirely, dynamic spawning or not.