I don't know how players play on Private Servers, but I know from general knowledge that on official Blizzard they "Optimize" the play and remember hearing about Raid.io which pulls info if player XYZ played "efficiently" aka if he is a Die-Hard that should be doing anything else than play RPGs, let ...
Got to say, don't understand the appeal of PVE servers, outside of Hardcore and RP. They make no sense to the lore with which this game launched, I mean look at the actual Intro Cinematic, the name itself.