[GSM]

I'm gonna be the odd one out and disagree here. Buster Cannon, at the very least, has some additional costs associated with it. Steel Body is a cheap 3M skill that can be used over and over, and will probably become more useful in the future anyway.

This is a drawback akin to being Knocked Down. This is saying BKs need to learn how to dodge Buster Cannon (which is hard because most BKs are pure tanks), they need to waste 3M every turn they're hit with Buster Cannon in order to keep their defenses, or let their defenses be shredded apart and picked apart by the Arbalest.

EDIT: I also do want to say that there should be an immunity portion to it- given that BKs are all about their tankiness, why isn't their defense-restoring thing also preventing it from happening further?