I'm not entirely sure if this has been posted or I'm posting this on the wrong forum but if there are some issues please feel free to write so.
Recently I have been traveling to the Ironclaw Factory and every time I get there there would be a HUGE lag fest with my party members and I! It get's really annoying that you would swing your avenger and try to shield cancel but then LAG SPIKE you get hit two times before I begin to move again. My teammates also experience this. Even when I solo Ironclaw Factory I experience Lag spikes. I try to fix this by setting the game options to low graphics and closing all other windows. I don't know if the problem is because of the connection I have with my internet or My internet provider.
Its the sheer prop count (ie the Rockets) on the level, mixed with the single threaded behavior of the JRE that kind of overloads it. Graphics settings won't have a major effect on it, so your only option is to either raise the thread priority thorough the task manager to above normal, and lock it down to a single core to clear the overhead from thread scheduling. You can also force a larger heap size through the JRE global settings, but if you use Steam, the process is a lot more complicated.
This is only a big problem on lower end CPUs, since higher end ones tend to have enough head room to eat the workload and keep going.