As far as I can tell, the slower the connect the better.
It seems as though the arena servers are not capable of maintaining substantial throughput and the faster you deliver data, the harder it is for AH to deliver back reliable computations. Hence the noticable increase of warps, rubber bullets, and other irregularities when the arena 's population exceeds 100 or so players.
I'm no engineer but I can tell that despite all the mumbo jumbo about PL, background apps, driver versions, vid chipset types etc. it all boils down to the amount of traffic through the server. If you can play reliably one minute, and the game becomes unplayable the next, it's mainly due to server load.
Since your in a timezone that encourages you to log at "off peak" times, you could probably get away with a coupla cans and a string.
If your setup plays ok, don't sweat the slower connection.