Guilds did inform BW after testing, that although they loved the fight, they felt it was a bit too hard for story mode. But maybe BW wanna see for themselves how the rest of the playerbase finds the boss, whether they struggle for long or not. They did change certain mechanics and increase enrage timer to make it easier.

I won't be surprised if it does get nerfed in future ( just this fight, the rest seem more forgiving). But in general they stepped up the difficulty a little,but I do think its reasonable. They also don't want to make it too easy that it becomes boring, and also makes the jump from story to hm too big. Since believe it or not, even casual guilds like to do story and then progress and try their hand at HM.