I wouldnt say hlog is a complete mess. I think most will go blocky if you zoom in enough. Even mine which at face value looks a lovely smooth like shows some blocks if I zoom in to show the first 1000 tones.
The longer the line the more blockyness there will be as theres a shorter distance to map until the signal fades so therefore the steps become more pronounced.
The area of concern is tones 180 - 270, particularly those around 260. Not sure what that is, could be a bridge tap, but if you follow the general curve of how the graph should plot, there isnt really that much of a deviation. Its attenuating tones 256 - 263 by about 8dB. Which could probably mean the loss of a few kbps.
However.. compare to your bit load. Its extremely hard to judge anything in this area due to PSD masking which will affect tones > 500. It looks like that tiny blip in your hlog has little effect on your overall bit loading.
Problem with vdsl on long lines is that PSD masks, mean not much bit loading goes on in the tones normally used by adsl. Very long lines which are only capable of using the D1 band dont really benefit from VDSL as much as shorter lines.
I find your QLN more interesting. There's some lovely signs of crosstalk going on... plus some RFI.
