It's not you, it's iburst. I am in a similar position, was quite happily playing WoW with an average in game latency ~700. Since mid/late January it's become unplayable. Don't have packet loss but the latency is very unstable.
Which tower are you on?
Tonights pings... all over the place
Pinging
www.iburst.co.za [196.30.31.120] with 32 bytes of da
Reply from 196.30.31.120: bytes=32 time=51ms TTL=124
Reply from 196.30.31.120: bytes=32 time=320ms TTL=124
Reply from 196.30.31.120: bytes=32 time=459ms TTL=124
Reply from 196.30.31.120: bytes=32 time=94ms TTL=124
Reply from 196.30.31.120: bytes=32 time=238ms TTL=124
Reply from 196.30.31.120: bytes=32 time=248ms TTL=124
Reply from 196.30.31.120: bytes=32 time=367ms TTL=124
Reply from 196.30.31.120: bytes=32 time=156ms TTL=124
Reply from 196.30.31.120: bytes=32 time=131ms TTL=124
Reply from 196.30.31.120: bytes=32 time=241ms TTL=124
Reply from 196.30.31.120: bytes=32 time=160ms TTL=124
Reply from 196.30.31.120: bytes=32 time=189ms TTL=124
Reply from 196.30.31.120: bytes=32 time=173ms TTL=124
Reply from 196.30.31.120: bytes=32 time=97ms TTL=124
Reply from 196.30.31.120: bytes=32 time=307ms TTL=124
Reply from 196.30.31.120: bytes=32 time=228ms TTL=124
Reply from 196.30.31.120: bytes=32 time=92ms TTL=124
Reply from 196.30.31.120: bytes=32 time=271ms TTL=124
Reply from 196.30.31.120: bytes=32 time=189ms TTL=124
Reply from 196.30.31.120: bytes=32 time=383ms TTL=124
Reply from 196.30.31.120: bytes=32 time=233ms TTL=124
Reply from 196.30.31.120: bytes=32 time=72ms TTL=124
Reply from 196.30.31.120: bytes=32 time=402ms TTL=124
Reply from 196.30.31.120: bytes=32 time=186ms TTL=124
Reply from 196.30.31.120: bytes=32 time=100ms TTL=124
Reply from 196.30.31.120: bytes=32 time=90ms TTL=124
Reply from 196.30.31.120: bytes=32 time=118ms TTL=124
Reply from 196.30.31.120: bytes=32 time=56ms TTL=124
Reply from 196.30.31.120: bytes=32 time=156ms TTL=124
Reply from 196.30.31.120: bytes=32 time=111ms TTL=124
Reply from 196.30.31.120: bytes=32 time=299ms TTL=124
Ping statistics for 196.30.31.120:
Packets: Sent = 31, Received = 31, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 51ms, Maximum = 459ms, Average = 200ms