I’m torn on PvE vs. PvP, because I have good memories of open world PvP in vanilla, and horrible memories of it from Burning Crusade onwards.
I do think we should stick to the same server though. The idea of splitting servers was originally a thing to support PvP, to try and avoid accusations of cheating. However, that concept dates back to the days before voice chat was almost mandatory. NOW, in 2019, the argument doesn’t hold much weight, since if anyone really wants to do that, they just make a shadow guild for the other faction, and coordinate over voice chat.
There are benefits to being on the same server, beyond just seeing each other logged in. Wouldn’t it be fun to organize an OTG Alliance vs. OTG Horde battle, where both guilds agree to meet at some specific place in the game world and try to “capture” territory? A virtual king-of-the-hill contest where everyone tries to hold some isolated hilltop for 15 minutes maybe.
Or just a footrace where both sides agree to NOT fight, but race through a bunch of contested zones and see which guild “wins” by being the first to reach the target? Nothing like that can happen if we split and divide ourselves across server boundaries.