I think it’s hard to find concrete data on this. Some websites don’t seem like they’ve been updated for years “Some still don’t even have DH on the class list” and others don’t show where they’re getting their data from.
It’s also a harder question to answer that it seems. What quantifies a “played class?” If I go and do a /who request for each class at max level on my realm, do I count people afking in Oribos and Stormwind?
Anyway, I’ve done just that over the course of months, because this is something I’ve been curious about myself. Taking all players at max level online at any given hour on my server, the consistently most populated classes are: Druid, Hunter, Paladin.
This doesn’t take into account which classes are actually seeing play in meaningful content, like M+, Raids, or PvP. Using the same /who method each hour as I did previously, Rogues were one of the least “played” often not even returning 50 results for level 60 players. Yet, if you do any BGs or Arena, you know rogues aren’t exactly an uncommon sight.
I think unless Blizzard releases the data themselves, it’s always just going to be speculation. But I think a reasonable guess would have Hunters somewhere in the top 3.