It is set at 325 currently and has been that way for a long time across multiple games. 500 would be pushing the capacity for the engine to keep up with network latency, but 325 is a fine cut off point. What issues are you having, because I have none when gaming?
ISP's are not always perfect. I had internet backbone issues for over a year before they fixed it. Turned out to be a faulty gateway in Virginia (which I don't live anywhere near), but it was one of the hops to get to the server I played on a lot.
Yeah, the server seems to be having some lag spike issues again like it did a few months ago. My ping was spiking from 80 to 170 randomly, and it seemed like it happens to everyone at the same time.