Hm, that is a good point. In theory, Focus was designed to benefit the person using it slightly more than other people, so that it's your go-to when things are going badly for you, but not so much for the other two. I'd have to playtest a bit, but I would lean towards a soft penalty where each time you use a move, you take -2 to the next use of it; you can still spam it if you need to, but it gets less likely to succeed.