Yeah not removing the mega server lock was a mistake as for PVE to PVP I called this a few times, the one after it happened after seeing repeat cry for PVE to PVP was here:
Everyone on pagle is jumping to benediction now - WoW Classic / Wrath of the Lich King Classic Discussion - World of Warcraft Forums (blizzard.com)
Where I said way back then:
“At this point, I’m mostly just looking forward to seeing the crying over the queues in pre-patch or with Wrath from these entitled types because unless Blizzard changes something drastic with their code there will be 4-hour queues.”