I think the record sellings have more to do with the fact that we've been waiting for so long, expectations were so high and so on... All because of Diablo 2 reputation. The game has come a long way since release... Spam chest runs and Nether tentacle DH farming blue weapons in act4 weapon stands. To now spam rift keys farming easy mob type with high density and Pylum / bosses.
I still get some enjoyment at the start of each season. The initial item hunt keeps people coming back for a short period of time, but eventually dies out to the usual emptiness.
Good game overall tho. Better than a lot of stuff out there, just didn't leave to the expectations that's all..