Oh, man, the memories. I remember this boss was the one that started to make things difficult for me. A wake-up call from all the easy enemies I'd fought before.
My assumptions on this battle; The boss itself is NOT Kurt Zisa, but Nitori. Kurt Zisa gets stunned after taking down a health bar's worth of HP, thus leaving Nitori to attack. Nitori probably has a reasonable amount of HP. A well leveled/geared Marisa can probably take Nitori down within three-four phases. The Mech in question probably changed with each phase.
My assumptions on this battle; The boss itself is NOT Kurt Zisa, but Nitori. Kurt Zisa gets stunned after taking down a health bar's worth of HP, thus leaving Nitori to attack. Nitori probably has a reasonable amount of HP. A well leveled/geared Marisa can probably take Nitori down within three-four phases. The Mech in question probably changed with each phase.