They have an Achilles heel though.
Would you want to invest all those points (and money) into a unit whose weakness the Rebels will surely learn to exploit?
It's going to be quite a task to get the balance right. We don't want it overpower the battlefield, or all we'll see are AT-ATs vs. AT-ATs (most everyone wants to win, win, win). If it's too easy to bring down, it will either be seen as a glass canon or feel neutered. Not much wiggle room there for the game designers.
I don't see it as a worthwhile unit at present. Until we know more about the game, other units and expansions, I just see the AT-AT as a nice idea that isn't very practical on the table.
Edited by Force Majeure