The one change that will bring back the players
Fix auxiliary gems. Make the effects match their own rank.
Players spent several thousand dollars ranking up yesterday's gems (void spark, wolfheort, etc), only to see newer players outmatch them with lower ranking newer gems. Power creep is understandable but too many have quit over this spend fatigue.
The good news is that a system is already in place. Many would return if a couple of bundles could bring a new gem to rank 5 and let it keep those R5 effects as an auxiliary gem. Whales will still keep whaling new gems to rank 10, and the server will be repopulated. A win-win.
It feels like Blizzard would rather watch players quit than offer a reasonable mid-tier path to stay competitive. Truly sad and pathetic.