Dawn has already been to Vesta...
Most Solar System formation theories posit that the planets have 'moved' since their formation. In this case, Ceres and Vesta are surprisingly different given the expected homogenous origins of the Asteroid belt.
Dawn measured Vesta at 3.5 gm/cc3 (9% of the Asteroid belt mass). Ceres is about 2.1 gm/cc3 (31% of the Asteroid belt mass). Pallas is 2.8 gm/cc3 (7%).
That is 47% of the Asteroid belt mass with each chunk have very substantial differences. If you are looking for breakup of a single item, these disparities argue against it.