From what I recall, each team combiner are united by at least one thing they all believe in / have in common. For Defensor, it's the desire to protect and save that's present in all five members, in Predaking it's the love of the hunt, etc. A single agreed-upon goal seems to be the glue that holds a gestalt together, which is why so many of them seem to be single-minded to some degree. Victorion seems to hold together better than most, I'd assume her team are closer than average with one another.
Pic related to thread and post.