First of all I want to say I am really enjoying the test. PvP is player-versus-player again, not Player versus proc or "Vate beam break olympics".
Cheers to everyone who are pissed by this change. You just need to spend some more time in this game to understand why this is so good for pvp.
Now to the other aspect -
lag. It is pretty obvious now that we had severe lag last night despite the procs being disabled.
I have no idea how much ZoS are playing their own game, but I am doing pvp every night.
I would like to discuss here thing that I as a player have noticed about the lag, maybe it can help identify the cause.
1. Lagging ususally starts when we have all factions poplocked an we have queue. If it is
/// , locked, locked, there usually is no severe lags. Some occasional hiccups and delays but still pretty playable. When you have to queue for it however, it is usually pretty unplayable.
2. I tend to first notice the lag on objects, that the server is understanding as "NPCs":
- Siege weapons take a few seconds to fire - after the initial button press it takes 1-4 secs for it to fire;
- Keep/resource npc position get's screwed up. Everyone can target an npc, but no one can really deal damage to it apart from big aoes. After up to 10 secs the npc gets teleported to the coordinates server was thinking it was standing, then you can kill it;
- Keep doors, walls. Breached doors/walls take their time to break and crumble after being damaged to 0 HP. Again - it can take quite a few seconds.
It can also happen if you are trying to enter a door. It reacts after a few seconds, that's why we get frequent "Double doors" when it's laggy. Cause we spam that button 
- Interacting with merchants is very delayed too, just like the doors;
- Pets get very drunk during the laggy time too. Blast bones, sub assaults (that too! we get slo-mo animations and even more delayed damage), sorc pets etc have trouble pathfinding.
3. Only AFTER I notice the weird behavior in points 1. and 2. I start noticing delays in my skills, barswaps and such. We start getting rubber banding and players teleporting after a ping spike.
If I have missed something - please feel free to comment, I will edit my post to keep it updated.
My personal suspicion is the lags are caused by, let's simply put it like this: Too many npcs are engaged at one time, be it actual npcs, ballistas or keep doors.
Anything that has a behavior determined by some sort of AI.
It works well when there are 30 people in Cyrodiil and every npc can simply follow their pre-determined paths. But it all changes when npcs in several capturables have to react - every NPC at Rayles outer is aggroed, when there are 20 ballistas at Chalman and a second breach on Ash wall.