It's unbearable to do the end of the campaign alone, the witch queen doesn't stop using her superpowers, she keeps sending one after the other and for us PS4 players, it's horrible to do alone and especially with the titan class. Apart from that on PS4 consoles, the gameplay is horrible and it gets worse.
It was a hard fight, a 4hr boss fight for me solo on legendary. But that's what legendary is for, it's supposed to be difficult to the degree that you have to change your load out from encounter to encounter and plan ahead, but when you do finish it, there's a major sense of accomplishment. If you want a more cinematic and casual experience, play classic.