A single correlian corvette would destroy most of those 6 tie bomber squardons before they could get in range of the Mon Cals. And I will target the engines on one or two of the ISDs first thing with my Y-Wings. If the Empire suddenly decides to retreat then the ISDs are lost. I don't see what people are whining about.
You got the point if you force the large fleet to retreat. However with instant repairs you will not be able to incapacitate the large fleet by just dammaging some hardpoints of bigger capital ships. Either you will have to destroy completly the ship in raids (which will force you to use larger forces) either you will not launch such kind of attack at all.