New forum, so I'll jump in with a new post on this.
We won't be adding a different difficulty tier at this time. Raids need to continue to remain the most challenging content in the game, and they aren't designed to be accessible by everyone from a skill perspective. Could they be more accessible from a "finding 9 other players to play with" side? Sure. That isn't always an easy problem to solve, and any solution would detract away from the team making more raid content. We'd love to get more content out to you guys faster really.
I see a lot of comments about W4 difficulty, so I'll add some notes on that as well. Balance came in later than expected since we had far more bosses and content to test than usual. Are we totally happy with how balance turned out? Yes and no. The Mursaat Overseer base difficulty is too easy, but we were very happy with the CM difficulty. For the next release we'd like to get difficulty tuned more back in line with Spirit Vale. However, some of that original difficulty and magic is hard to re-capture. You never forget your first raid boss kill.