I don't know if that was discussed earlier but If you really plan to keep going with this drm content, could you please consider getting rid of those extremely boring, uninspiring and time consuming pre-events. At least for CM's. They add no depth, provide no challenge, and are just there to waste your time. It's just really discouraging to keep repeating them over and over just so you can fight the boss again.
If it was some kind of dynamic diversified events, I guess it would be more bearable, but then again it's an instanced content, not an open world area where they occur naturally and may take different forms and completion approaches, which makes it way less repetitive and more engaging. Fractals are a great example, where you can actually choose to skip the pre-events, given you have the right build/gear/class/items, which makes it less dull and actually more entertaining.
Like really, they are totally fine for the first clear when you're engaged in the story progression, but as a repeatable content... I would love to fight the boss again and interact with new mechanics, but having to waste my time on those stale identical pre-events makes me want to quit it. Just put a standardised timer on the boss and give everyone who unlocked the masteries the stat boost, because they will get them ANYWAY, since there's virtually no challenge in completing the events, except if you value your time.