I think it would be nice if it had the "all bosses" category, since besides the normal ones there is also Mileena, Kano and Ermac ...

yes please

The only hesitation I have with an All Bosses category is that it doesn't really add much to the run overall. The routing changes very little from "All medallion" runs in that it only really adds extra backtracking. There's also the issue that it will need 6 categories for just All Bosses since the No OoB/OoB Normal/Hard Solo/Coop splits will still need to be made. I'm not sure we have the player base to justify that much more clutter at the current time.

worse that is true.....