Would it be pointless to have a mbp 13 inch with a 12.9 iPad Pro? Or better off getting the 15 mbp to go along with the iPad?
Is kind of pointless. Normally you'd use an iMac and an iPad, powerful computer for the desk and powerful tablet for portability. You've chosen to have two portable options. However it really depends on what you intend to do with them, which you didn't state.
I move around a lot so don't want to haul a desktop computer, but I would like a powerful portable device. I do need the MACOS software as I cannot completely depend on IOS yet, but I would prefer a IPAD when I do travel around for work. I know its not the best financially choice!