I'm so glad you asked this question.
We’ve seen some confusion about layering, both about how it helps support our launch, and how it’s supposed to behave while its active, so I’d like to both speak to it and clear up some misconceptions about it.
First, we’re absolutely committed to reducing to one layer per realm before our second content phase goes live, and the sooner we can get there, the better. The reason we can’t do that initially is that on launch day, everybody will be clustered in the starting zones, and having players so close together causes an exponential drain on server resources. In fact, the same number of players cause more server problems crammed into Northshire than they do spread across all of Elwynn Forest. We expect that even after the first couple of days, we’ll need fewer layers than we need for the initial hours of launch, and our stress tests have confirmed that expectation.
A related concern that was raised during our pre-launch test was that capital cities felt empty, but that only occurred because we left the pre-launch test running two days past its original end date, and we didn’t reduce the number of layers at all during that test. During our launch week, as the players spread out across the world, we’ll monitor activity and reduce layers as necessary, so the world continues to feel full.
Some players have suggested using sharding in low level zones to address launch demand, both because we talked about that at Blizzcon, and because it’s what they’re used to from our modern expansions. Unfortunately, while modern WoW has content designed to work with sharding, WoW Classic does not. The most obvious example of incompatible content is Rexxar’s famously long patrol path, but there are lots of other examples throughout WoW Classic. Since we want all that content to work as it was originally designed, we’ve made sure that every layer is a copy of the entire world, so you can kite Anachronos all the way to Orgrimmar, and you can ride the boat from Ratchet to Booty Bay with the same people alongside you the whole way.
Some players have asked us to use realm caps and login queues to handle the demand, and while those are tools we have at our disposal, we don’t want to rely on them exclusively, because they keep people from playing the game.
One of the most frequently reported problems during our tests was players transferring to a layer for what seemed like no reason. There were several bugs that caused this, and we’re confident we’ve fixed them. At this point, the only thing that should cause you to change layers is accepting an invite from a player on another layer. Additionally, it should always transfer the player who was invited to the layer of the player who invited them.
Nonetheless, after accepting an invite, the layer transfer doesn’t always happen immediately, because we don’t want to transfer you in the middle of combat, or before you get a chance to loot. During our pre-launch test, we saw a few reports of what seemed like random layer transfers, but when we investigated, we realized this was due to us making that transfer delay too long. The delay was so long that players could unintentionally chain one delay into another by starting combat immediately after looting. Because of those reports, we’ve fixed the transfer delay to give you enough time to loot, without being so long that you’re left wondering why you can’t join your friend. We’ll keep an eye on that, and we may decide to reduce it further.
We’ve also seen reports of people transferring suddenly at the entrances to capital cities, which was related to the transfer delays. If you’re waiting to transfer to your friend’s layer, and you enter a capital city, we ignore the delay and transfer you immediately. The long delays were making it more likely that you’d enter a capital with a transfer pending, and now that we’ve reduced the transfer delay, it will be a bit more clear that your transfer was the result of accepting a group invitation.
Regarding PvP, we saw many posts from players wondering if getting invited to a party is a good way to escape from PvP combat. I’m pleased to say there’s actually a separate, longer transfer delay following any PvP combat. We know a lot of world PvP enthusiasts are excited for WoW Classic, and we don’t want the additional layers to feel like they’re robbing you of your kills. When the time comes to withdraw from the fight, you’ll have to escape from your enemies and get to a safe place before you’re able to join your friends on another layer.
I’d also like to clarify how multiple layers work with logout. Early in our stress testing, players reported that logging out and back in would let you hop to a new layer to farm the same mineral or herb node on different layers. That was a bug, and we’ve fixed it. Your layer assignment now persists for a few minutes between logouts, long enough that by the time the game would choose a new layer for you, that node would have respawned on its own anyway.
I hope that all makes things a bit more clear.