Most feats are overpowered relative to the alternative, because they're balanced against a +2 in your primary stat, which means any feat that you can use is flat-out better than +2 in any other (non-primary) stat. Once you've capped your primary stat, any feat you can use is a pure power boost. This feat just happens to be one which can benefit anyone.
In the base game, if your fighter wants to increase its Wisdom save, then you take Wisdom +2 at your next opportunity. Once feats are available, your fighter just takes this feat instead, for roughly five times the benefit. If you can take the feat twice, then you're even more overpowered than you would otherwise be.
So yes, it would be broken to let someone take this feat twice, but it's already broken to let anyone take it once. It's just a question of degree, on how broken you want your game to be.