I understand and appreciate Bungie's effort in D2 to move away from bullet-sponge bosses, but this is entirely the wrong way to do it. The boss fight is ruined by his constant disappearing making it impossible to feel engaged as he just disappears for large stretches of time and leaves you standing there. For Nightfall the Attrition Modifier works terribly with the fight. I don't mind modifiers making strikes harder and like the challenge, but this was not done in a fun way. Instead it forces you to get a movement debuff every time you want health. You spend the whole fight crawling around, constantly on low health and almost never seeing the actual boss you're meant to be fighting (whenever you do find him he just leaves again after 10 seconds) all the while futilely watching your timer tick down as you wait for the boss to start feeling like he wants to be in the game.