TLDR; right click on each d2r.exe in taskmanager, and select efficiency mode. You probably dont need BES or to run anything extra.
multi instances of Diablo II Resurrected can cause occasional system “freezes” because each client uses a very aggressive render loop that wakes the CPU constantly, generates frequent GPU interrupts, and runs at a high priority.
When multiples of these loops run together, they can overwhelm the Windows scheduler, starving critical system threads like the Desktop Window Manager, GPU driver queues, and Winlogon—so the screen stops updating, Ctrl+Alt+Del won’t respond, and the system appears frozen even though it’s not crashed.
Efficiency Mode fixes this by lowering the game’s scheduling priority and applying EcoQoS, which reduces CPU aggressiveness and prevents the game from monopolizing CPU time.
As a result, essential OS threads always get enough time to run, and the system stays responsive even under heavy multiboxing load.
Windows 11 is more susceptible because its newer, more aggressive scheduling (intel hybrid architecture) can starve critical system threads under heavy load, whereas Windows 10’s simpler, less dynamic scheduler tends to keep OS and driver threads from being pre-empted.