Back in Destiny 1 we had a heroic strike playlist that was a bit harder than regular strikes. They were a lot more fun. Reminded me a bit of Spartan Ops from Halo 4. The feedback from the legendary campaign showed that people do enjoy higher difficulties in Destiny 2. And maybe a "Duality is too hard"-Problem could be avoided if such a playlist existed. It could serve as Training Ground for future harder content. Doesn't even need additional mechanics or champions. Just higher/fixed level scaling. We players feel barely powerless (aside of the campaign) and that is one of the reasons why some people complain about difficulties being "too easy" or "too hard". We lack the middle ground, a step on our stairs of difficulty.
I would love this. Challenging content is fun content. One of my favorite aspects of WQ was the legendary campaign. I wish it had continued into the seasonal story missions.