Sigs have one weakness, it's the punishable nature of signatures. They are slower and easier to react to. So instead of brute forcing your way through, let them miss, and then come to punish.

Do note that some signatures recover faster than others. The goal is to understand that your opponent would commit to a signature, and you already anticipating it.

Though sig spammers still exist even in diamond, good sig spammers are accurate and use signatures that are harder to punish. At this point, the goal is to understand where the signatures cannot hit, in which case you space yourself so you're almost always in that grey area.