Slightly evil thoughts here.

I wonder, since pos hacks exist, if it would be possible for some clever programmer to develop a 3rd-party hack that would just read your current location according to the client and force it along to the server more often. Say, 25-100 ms instead of 300 (only when position values are actually changing; it'd be stupid to ramp it that high when you're standing still).

I'm sure if that were possible, it would be very problematic if it became popular (the increase in incoming traffic would likely not be good for their servers). But if it helped alleviate the issue, it would also be pretty clear evidence that 300 ms is far too long a wait.