From what I have read the rubble asteroids are the hardest to do something about. We can redirect a lump of iron provided we have enough warning, but rubble asteroids are much trickier since you cant just push them out of the way. The only two options are gravity tractor or demolition. Neither option is easy and both require lots more advanced warning compared to a similar mass solid asteroid.

Bunker busters wouldnt be particularly useful since the warhead wouldnt survive the impact at the speeds necessary to get sufficient penetration on a rubble asteroid big enough to need redirection. The drone idea is harder, but if you can get several deep enough with big enough bombs the blast should at least nudge the thing off course.