Sources of lag:
- Local machine fail
- Server fail
- Network fail
That's it, basically. Either a local resource (CPU/GPU/RAM/HDD) is pegged, a server resource (same set) is pegged, or the connection between the two is pegged.
I think one of the key points brought up is that 300+ people being active in the same area at the same time requires a whole lot of server-side processing - I think the word "exponentially" was used. I know that Rift attempts to mitigate this by loading your raid with priority - and extending this concept further might help. As in, if Trion were to:
- Hide everyone not in your raid from you (or maybe just full raids)
- Communicate only the raid aggregates to each other raid (so you'd see only "RAID 4 does 18k raid damage and 6k raid healing this second")
- Figure out a way to handle item use (like the turrets), public group joining, and PvP flags elegantly
Dealing with 40 "actors" in a zone is pretty easy for my client. If 20 of those actors were other toons (in my raid), and the other 20 were raids (representing 400 other toons), things would probably run more smoothly across the board.
They might even consider using the ground render radius to show people in my immediate vicinity, if the above technique opened up sufficient resources.