Since Blizzard only understands the language of money, (and they objectively suck at longterm investments) I will give arguments for introducing cross-server functionality or server mergers.
Mop has the potential to bring in the most players to classic wow, being a beloved expansion to a lot of players, rivaling that of wrath. However, with the current handling of servers, this is going to end up being far worse - possibly worse than any other expansion.
With the current state of server populations, where most if not all servers are monofaction, people aren’t going to stick around as long as they would. This is a revenue loss from early sub cancellations.
Returning players that are hyped for MoP, but are stuck on a dead realm, or are the wrong faction on a monofaction PvP(lol) server, will NOT pay for a server transfer. They would rather suck it up and not play(people are already used to the idea of giving blizzard the middle finger) than actually transfer - yes some people will transfer, but its overall a net loss compared to the gain you get from stable subs for a few months.
Merging the PvP servers will create a balanced megaserver. Yes, some PvErs will be mad that they might die(shocker) on a PvP realm. This is where the real cashgrab kicks in - PvErs are more likely to pay than PvPers for a server transfer. They will transfer off to their PvE realms, leaving the PvP realm playerbase healthy(at least for a while). After a couple weeks the servers would be locked to transfers once more. And this is where cross-realm would kick in as well, largely preventing the problem from reoccuring.
Cross-realm was already a part of MoP originally, and not seeing it implemented simply isnt “classic”. I understand the ideas against introducing crossrealm, I hate it myself, but with the current server issue, there really is no other choice to keep the game stable.
Getting ganked? Get your friend to invite you to their healthy(er) popped server. Or invite them to even the odds! Got a problem finding raids cuz your faction on the server is dead? Np, someone can cross-server invite you. If those options arent there, i’d rather unsub and go play on a private server, for free, with more players, with better customer support, and no botting.
Blizzard, don’t be stupid, and do something productive for once.