User blog comment:JustSomeDude.../Law's Plan & The Shichibukai/@comment-4754162-20130204062632/@comment-3425840-20130204175920

I think the idea of balance is not linear here,

The mairnes are undoubtedly more powerful than a single Yonko crew or the Shichibukai combined however since they have to deal with lots of stuff, the effective focus they can deliver to the Yonko section is < One Yonko + allies and thus they require the Schibukai support.

I agree that combined Yonko is not a valid idea as they are individual entities not a whole one.

Think of it, all the marine in all the world can crush any single Yonko and allies however that is not a very convenient method and thus they deployed fraction (bigger) of marines in cahoots with  Shichibukai to take on Whitebeard (example.

Similarly, the combined might of more than one Yonko (and allies) acting together can take out the entire marines (note, not the entire World Government but only the marines) and even deploying the Shichibukai won't probably be enough to stop that.

The whole scene is pretty complex.