To be fair, the Empire would have made a much cleaner sweep of the Rebels if Captain Needa hadn't screwed up. And if the Rebs hadn't had that planetary ion cannon stashed away.
And if Admiral Ozzel didn't come out of hyperspace too close to the system... but one reaches the point we're sort of making a lot of excuses for the Imperials here, no?
To get back to the Bolos for a moment: Any Empire that could build a Super Star Destroyer can surely build a Bolo-class tank which would not only be faster than AT-AT, but the later models would have ground an AT-AT underfoot, have considerably more firepower, and trundle right through the forest, rivers, deserts, ice, and really hostile places like the surface of Venus with ease. AT-AT's look cool, but in reality even an A-1 Abrams would outmanuever it and maybe take it down. Treads are never going to go out of style.