I could knock him down to 70% health no problem, but then occasionally I would somehow "miss" the zandatsu of a vehicle he threw, that takes off ridiculous amounts of health on hard. I threw I don't know how many EM grenades at him and never had it hit clean for the longest time so I didn't realize that was how you needed to make it so you could hit him once he started the magic pieces bullshit. I finally start getting it down and on a good run would get him to 40% or so; then he pulled that Lorentz force crap; I swear that shit took 50%+ health when it hit me... combined with the random "i can't see stuff off camera, but hey, it hit me for 5% after it crashed" bs, that took forever.
Mistral wasn't bad. My health was low, but I managed to beat her on the first try. Monsoon took me over 10 tries, I think, possibly more.