Aetheric Density duty/level/etc list?

I thought I read somewhere that various things beyond dungeons now give you density (I've been getting some from a single Frontlines roulette each day), but I can't seem to find an official (or at least accurate) list anywhere. Does such a thing exist? Forum search isn't turning up anything useful. Thanks!

Edited to add:
Part of the reason why I ask is because I did get some from a solo run of Wander's Palace (Hard) and that was added in patch 2.5, so it's not just HW content.