It's weird that Dice's response to Rebels winning pretty much all the time, is to remove TIE spawns from tier 3. But aside from the balancing issues for the Empire, it also took out the rush & fun of dodging enemy pilots and hoping you would be able to get at least one down, or sometimes even clutch two. The latter however was a rarity and a good job by the Rebel pilot.
Now pretty much every game (if we haven't lost walkers in earlier tiers already) is mopped up by the Rebels in tier 3. AT-STs as anti-air simply isn't effective if Rebels still have air superiority (through X-wings and A-wings still being up in the sky due to their heavy advantages over their TIE counterparts) as those vehicles will shred AT-STs before they get to a proper position. AT-STs also are way too weak, and are generally destroyed insanely fast by any competent team even if they only have ground units (vehicle turrets, rocket powerups, ion torpedos etc.).
Pretty much every game I am standing at the AT-ATs in a futile and last ditch attempt to use my goddamn blaster to shoot at the airspeeders in the hope that it screws up their minigame. But it's hopeless as there are multiple of them and if you get shot once, then the Walker is probably down before you respawn.
I have solely been playing Walker Assault since launch and still having a blast. But these changes made it less fun for both sides, making it even harder on Imperials and a lot easier for Rebels which takes away any sort of satisfaction from actually pulling out a clutch win at tier 3