I'd expect at least one or two more fighter casualties, due to lawn-darts. Were I commanding the tanks, I'd split my fire and spread the clusterguns evenly, so as to force as many of those rolls as possible. Split the difference between our estimates, and four fighters dead leaves only two to go after whatever their actual target was, possibly not enough.
And while it sucks for the tankers, from a high command perspective, trading six tanks for gutting a squadron of ASFs is an amazing deal.