chevrolux: You must be quite a distance from the ISAM for sync speeds that terrible. Not surprising when you consider how relaxed Chorus are getting with VDSL - used to be a strict 10.8dB and now they just seem to provision it for anyone who asks for it.
As sbiddle mentioned, highly likely you have a dodgy pair. I don't really accept the notion that 20m of Cat5e/Cat6 from the lead-in to the modem makes all that much difference, I think that is just consultants with theoretical datasheets who came up with that idea. As long as there is a good quality piece of wire to the ETP where the splitter is things should be fine - note the wording, "good quality".
I believe the minimum service level for VDSL is 15Mbps download speed so Chorus either need to get it fixed or roll you back to ADSL2+ which will probably give you similar downstream rates but an abysmal 1Mbps upload rate. If I were you I would stick with the current 10/10 connection, that is what I want at my place!!!
should have really stuck to that 10.8dB... lines like this clearly show, atlest for downstream, VDSL isnt best.