Fix the lag&delay! I was today on almost empty server for an hour just right after maintenance... that was best time in ESO I had in last year. IMMEDIATE bar swaps. IMMEDIATE. Not after a second, not after half-second, you just press button and it happens instantly like in single player like in another action multiplayer games, it was like fresh air.
Lag and delay problems has nothing to do with "spaghetti code" or whatever. Game simply can't handle such amount of players. Make a decisive action, if possible greatly increase hardware resources if not then split mega-servers.