I don't find Battle Stomp to be overpowered at all.
IF you happen to have targets in rather narrow cone of average length..
..and IF they happen to have their physical armor already removed..
..and IF the attack is not dodged or avoided..
..then you can force impacted targets to miss one turn with a knockdown using an ability with a 4 turn cooldown (an ability that is already being used late in the battle due to the necessity of removing the enemy's physical armor first).
I've not been in too many battles where I've gotten to use it more than once.
On top of that, it removes elemental states in the impacted area, which can be a boon, but can also be annoying if said elemental states happen to be beneficial to your party or battle plan.
And unlike the claim in the original post, from what I've seen it does not affect targets on different elevations.
