I, too, would not chose the Sundara for anything electronic (there are a few exceptional tracks though).
For me Sundaras are all about natural instruments and timbre. Like acoustic, classic, jazz and very much vocals.
The Sundara has lots of details and a good soundstage, also very good imaging. But, in consent with previous poster, my main complaint with EDM (music with synthetic sounds mainly) would be the Bass. Dont get me wrong, Sundara does have bass, even deep reaching. But it is just not very 'organic' sounding, not embracing. Kinda hard to explain.. I think u would understand if u had them at the same time with some good dynamic driver to compare.
For EDM, Techno, Ambient etc. i go with my Denon AH-D7200 and AKG K245 which produce a much more satisfying sound for that matter.
However the Sundaras are still my favourites HP's overall. They do something undescribale, that no others do.. But i havent heard any TOTL HP (and i dont plan to yet, i want to stay with what i have for now).
Edit: i just listened in on some of your drone music albums and they all seem to be not featuring a lot of bass. So the Sundara could be worth a try for that. but nonetheless i find sundara to be tuned too brightly for that kind of music (u can always eq though).