The campaign co-op lag been fixed on the 360 yet? it was horrendous last time i played
The lag in the game is primarily based on the host of the game you are running in. There is nothing that can be done to the game to “fix” the lag. You just need a better host.
To expand upon that, because of the fact the engine is 10 years old, the netcode wasn’t really going to be efficient. The game is always going to be laggy, simply because it’s so outdated.