While I do understand the desire for more challenging, lower player count content - regular roulette (despite being called expert roulette) will not be the place it is added. I know people don't like when other MMOs are referenced, but the early heroic dungeons in World of Warcraft's cataclysm expansion tried to bring back more challenging mechanics to its dungeon content and what happened was a tier of content that couldn't be completed by casuals, players sitting in queues for 40 minutes for a one-in-five chance of being able to clear the assigned dungeon.

The developer team has said in the past that they want dungeon content to be easily accessible to all the player base, which is a big part of why it isn't particularly challenging. The average skill level of players is surprisingly low.