Keep in mind that it was really a one-time tactic that was used early on in the campaign. The Yuuzhan Vong themselves said that it was such. Plus it would only work in a planetary setting, and not only do the Borg not confine themselves to a planet, but they would quickly adapt to meet the challenge.

I do believe that they would detect the gravitic fluctuations around a planet-smashing dovin basal fairly early on, anyway, and dispatch a team to investigate and assimilate it.

...actually, now that I think about it, the Vong don't stand a chance. D: Scary thought.