I tweaked the objectives every year, but I haven't done much with how the warbands fit. It is a subjective process trying to assign warbands that really don't fit. For example we stuck the Beastmen in the Scourge of the Seas a couple of years ago. (I should write a Chaos Objective.)
Oh, Tomb Guardians should not be able to be Celestial Canopy. They were only there because the original internet campaign allowed them and I was following its example (or at least I thought I was). Halflings were there for the same reason. Halflings should be Lure of Fortune.
Possessed, Tomb Kings (and Carnival, if I allowed the Carnival in our campaigns) can also be Silent Threat.