I tend to agree. For me, Kaine is the (traditional) Venom to Ben's Peter, but even more important to each other. I'd say the relationship each has with the other is the most important relationship each character has.
That being said, if Beyond is pushing Ben into some new territory and not focused on the themes that come with his status as a clone, then Kaine isn't particularly necessary -- because I agree that the focus then automatically becomes their relationship rather than one specific character.
I do know one thing: Kaine probably couldn't leave Ben alone even if he wanted to do so; and the longer Ben stars in a comic, the more apt it'll be for Kaine to show up.
-Pav, who wonders why Beyond wouldn't recruit both Ben and Kaine...