Imo the main problem is the fact that aug is the only support spec.
It is hurting right now because in raids deva is hardly doing more than aug damage. Sure in M+ devastation can do some ok numbers (still nothing, compared to rogues/dh) but if it can’t pump numbers in all content and be close to if not the best dps, why would wouldn’t someone prefer augmentation you know? Augmentation is so much more useful that it isn’t even comparable.
This happened to disc/holy priests and still does. People with blatantly refuse you for playing holy because it’s a healer that…heals. Disc is a healer that heals and does insane damage and provides damage reduction. And the dev/aug differences are much more substantial.