We're experiencing some very poor ADSL2 service suddenly. The router was swapped for a known working model at another site, so the next step was to look into the ADSL stats. Based on the stats below, if anyone could shed some light on the possible cause, it would be most appreciated.
A couple of the stats don't quite look right especially the downstream output power level. Note it's a TP Link so ratings are in .1 dB
SpeedTest results: Ping 545ms 2.2MBps UP and .10MBps down (varies widely)
Distance from the cabinet: Less than 100m
Relevant stats from the TD-W8960N router:

Router logs reveal a large number of the following:
Sep 17 08:38:53
user
warn
dnsprobe[1908]: dns query failed
Sep 17 08:39:57
user
warn
dnsprobe[1908]: dns query failed
Sep 17 08:52:23
user
warn
dnsprobe[1908]: dns query failed
Thanks for your assistance!