Avant-Garde is a broad concept, Roivas, and is open for debate...while many Industrial artists borrowed heavily from Musique Concrète, their fusion of its concepts with the intensity and presence of rock music not only helped it find a larger audience, but possibly helped give it focus. I agree that not all Industrial is Avant-Garde or very experimental in general ((
KMFDM, for instance, I would certainly not include here )), but a lot of what passes for Industrial these days is anything but. The original innovators of the style were still very atonal, abrasive, and experimental for their time in the late '70s/'80s world of rock and they influenced a massive number of future musicians. In general, I find that the incorporation of disparate musical elements into a new creative idiom is very much Avant-Garde, and quite experimental, even if it does include Rock music as a base ((
for shame! 
)).
Essentially, I believe that within each genre of music there is its own respective "Avant-Garde", be it Jazz, Classical, Rock, etc, all of which do not sit well within a single accepted genre and defy classification, and all these are welcome for discussion here. For acts such as Throbbing Gristle, Einsturzende Neubauten and Skinny Puppy, I consider them very much a part of the "Rock & Roll Avant-Garde" ((
however, for those who came after and followed in their footsteps, I would say less so ))...
...but as always, this is open to debate.
