It was a moment of great satisfaction to everyone in the raid.
It made me remember when, long ago, we downed Archimonde in Hyjal. Again, that was a fight which took a lot of work for us. We even had "remedial healer and tank training" days, where the dps was not brought in, and the only goal of the healers and tanks was to learn the required movements of the encounter enough to stay alive until the enrage timer. Once we could hit the enrage timer, we called in the dps.
It took weeks of orchestration, but those weeks of practice were what made the achievement of the goal satisfying.
When goals are too simple, their accomplishment does not bring this sort of satisfaction. This applies to real life, as well as any game. I had a teacher once tell me she did not want my daughter working on "+5" exercises, because they were more difficult for her. She wanted to keep her on the "+0" exercises, to boost her self-esteem. I told her that meeting and surpassing a challenge is what brings self-esteem, not repetitively performing simple tasks.
This is why I do not complain when the game encounters are difficult. I know that victory will taste all the more sweet for the price we had to pay along the way.