After roughly 100h of break in, the core signature of the K812 has not changed that much.
Having done a lot of further iterations with different cable arrangements, I've come to the conclusion that
- in stock form the AKG K812 doesn't provide the flag ship SQ its touted for
- the cable is in such a high degree part of the K812's SQ, both on the positive as on the negative side, that for me modding this can is not worth the effort, as the result will be totally unpredictable.
My guess is, that those who ventured into modding the K812 and put it on sale short after, have run into severe SQ problems not foreseen.
The "distortion" issue and also, that complex passages are hard to dissolve, are IMO highly related to sort of exaggeration of the K812 - fed by the original three wire cable - on the upfront edge of sounds. Thus, perception of more quiet notes in the mix get subdued to some degree. The original cable accounts substantially for that specific behaviour and IMO the three wire arrangement also accounts for left / right interference and less than stellar "3D" presentation, but on the other hand it also accounts a lot for the airy presentation and for a very special sense of quietness and clarity I loved.