Despite my general reservations on solo content, I'm okay with something like Visions becoming a permanent fixture. Its rewards, despite going up to near-Mythic level, were not plentiful enough to have a hugely negative impact on any of the other group content in the game and it felt good to go in and blast it away on each of my alts. Just get rid of the currency grind to enter and I'd love to see something like that added. (Torghast was close but they went about its reward system entirely the wrong way, imo.)