3 TIEs = 2 Adv when it comes to anti-ship dice. So the best way for an Imperial to match 8 A-wings is 12 TIEs and the TIEs should win. They'll take a beating, but they should win.
But at that point you will have a hard time supporting 12 squadrons with commands, and ties are much worse after an engagement since they'll likely be left with 1-2 hull after counters and be easy pickings for anti squadron ship fire, if they beat the a sings in the first place. Not to mention 12 ties is 96 points