However...

When you say a TIE Interceptor "wing," you are referring to the 66 remaining Interceptors on the surface, are you not? If I have the numbers right, you landed 25 AT-AT's and 36 AT-ST's, which would require 9 barges (if we assume you're using the Y-85 Titan dropship; if you're using the Theta-class AT-AT barge, which seems more likely, your landing would have required at least 43 barges). In either case, considering the number of troops you also landed (12,296), I'm assuming a significantly large number of transports spread out over a broad geographical area. This would be difficult for 66 Interceptors to cover simultaneously.

After all, if Acherin is approximately the size of Earth, 66 TIE Interceptors would mean 3/10,000,000th's of a starfighter for every square mile (3/10,000,000th's of a starfighter would be, I believe, one chip of paint, or perhaps a fleck of durasteel). Now there's a fun fact, but I digress.

Also, if we are being charitable and assume you had, let's say, 4 TIE Interceptors to cover this particular walker barge that was attacked, I'm not convinced that their lasers would have much effect on a CR90 Corvette's shields. Consider the Battle of Endor, where "hundreds" of TIE Interceptors were present. The Alliance fielded 7 CR90 corvettes, and only one is known to have been destroyed in the battle (this ship having crashed into a Star Destroyer, not the result of starfighter fire). That, and most sources that I know of seem to depict TIE lasers as rather weak or, at least, average. True, they could "destroy small asteroids in one shot," but that doesn't seem particularly difficult, and a small asteroid is certainly not the same as a deflector shield.

Also, and finally, it was stated in my post that the CR90's were "now with starfighter escort," which would have been present in this particular attack and (again assuming 4 TIE Interceptors, charitably) would have given them a run for their money.

But!

If you do still think that claiming four walkers as casualties isn't warranted, or is too much, I'll gladly edit it. I mostly refuted you in this post just for fun (and boredom), and despite this, it really doesn't make much of a difference to me either way. So let me know.