Given how dominant Yoho has been, his age, and his injury history, I'd call him up yesterday. Yoho is only ever going to be a RP, and seems more likely than most to have injury problems, so get some great airbendy MLB innings when you can.
Given Mis' youth, innings limit, and ceiling, I'd wait unless he breaks down the door. Calling him up now means burning an option next year, or losing a year of service time to keep him up. Given how few innings he'll be able to pitch, you better be damn sure those innings will be better than the alternative.