In accordance with embodiments disclosed herein, there are provided methods, systems, mechanisms, techniques, and apparatuses for diagnosing and optimizing vectored DSL lines. For example, in one embodiment, such a system includes an interface to a first subset of a plurality of digital communication lines allocated to a vectored group and to a second subset of the plurality of digital communication lines which operate external to the vectored group; a Dynamic Spectral Management server (DSM server) to analyze the vectored group by performing the following operations for each of the plurality of digital communication lines in the vectored group: measuring a mitigated noise level for the digital communication line with crosstalk cancellation active, measuring a non-mitigated noise level for the digital communication line with crosstalk cancellation inactive, and comparing the mitigated noise level measured on the digital communication line with the non-mitigated noise level measured on the digital communication line. In such an embodiment, the DSM server of the system further issues optimization instructions based on the analysis. For example, by issuing optimization instructions for the vectored group, for lines external to the vectored group, or for both.