I choose "other", but I fully understand that what I expected from champions might be completely different than what others expect or want.
I think of the hero units in Warcraft 3, that would level-up, have cool cast abilities, and general supplement your main armies (talking about about general skirmish, not specific campaign missions where they become the sole focus).
For the most part, they seem to fill that role. I don't really like that they insta-respawn, I think if you lose one there should be some kinda cost like a cooldown or whatever, but I understand that you have to support the mode of a champion-only player who might get bored waiting (of course, they could always just ally-control in the meantime...)
But I play from the perspective of a Normal+Champion, so a unit that is going to require constant babysitting is pretty much not going to appeal to me. Nebulae that require complete attention take too much away from other activities, and at low levels end up feeling like slog-fests (three way I'm looking at you). I wish that the champion "campaign" interacted more with the main one in the way that spire does.