Currently, entering Dungeons or Fractals is a simple procedure (always wining), and putting 10 together for Raids is complicated.
Do a hard quest for 5 (apart from the current ones) in that you DO NOT ALWAYS WIN, but where we have to work hard and put together a good team (tank, support healer, dps, explosive damage & varied support).
P.D.: The problem with Fractals T4 + challenge mode:
The idea is that it is a real challenge, and that motivates all to look for fellow specialists in his/her area (tank, dps, healer, etc). Make it a real quest, with real partners