This game is far to difficult.

[ruinedmirage]

how long does it really take to figure out what skills the boss is using? and how to deal with them?
i'm not expecting everyone to be all pro....but it's just memorizing simple patterns.

That's only a small part of the problem. The real question is, How long does it really take '8 people' to figure out what skills the boss is using 'and coordinate as a group'?

The rest of the problem is not taking the initiative to gather a static group, because going in with random players with random mindsets and random strategies each duty run will never end well. In fact, I'm gonna go the distance and say, if you don't want to form a static, you're not serious about beating end-game content.