Yosemite is new. There has been past issues with new OS's and Pioneer gear which have needed new drivers created/released (by Pioneer).
Try your setup with something that is not Yosemite. Also in the future, if you rely on your laptop for DJing, don't update your OS until Pioneer releases a driver or confirms if you need or don't need one for the OS you want to upgrade to. In this case, to my knowledge, there has been no comment yet.