A thought just came, what if you were using melee and Kree is your boss on the 5th world? Does that mean you are screwed?
None of the Shattered Worlds bosses have style resistances. We made a specific point of making it that way so that you don't have to carry all 3 styles in the event you run in to a boss that doesn't match up.
A similar example is we didn't add KBD because we didn't want people to take antifires every trip on the chance KBD might spawn.