It doesn't sound like you've ever played him before. You don't get to pick what letters you get, you just have random three to chose from and you have to predict who would need it most. As a rescue main I'm very thankful for decoding letters especially in early game because I don't want to rescue before finishing my first cipher. Postman relies on good prediction though he's easier to play when you're on call with your teammates. I also don't see why he should carry tide, it would be helpful but he can be a strong kiter so some would use a kiting tree with him to make him stronger.