One of those walkers goes down only because Luke is able to pop open a hatch on the unarmored bottom with his lightsaber, not a common cause of these being taken out for the Empire. If you discount this d/t the uniqueness of Luke and his talents then you have a 20% casualty rate.

I don't mind the idea of more robust impacts on the walkers who remain unaffected. The existing shot is fine and doesn't need to be changed. Things don't need to be changed for the sake of changing them, this is one of the two movies of the six that is largely fine as it is. "Improvements" should be done to address poor fx that were not corrected over time or to create something that couldn't be done at the time. What I've seen with the AT-ST's fits that, they were in the movies but nothing was done with them. Seeing them operating as walking flak batteries is a nice enhancement.