I would not say the learning curve is to steep if you do your IR before the cpl. The cpl is just a spiced up ppl, nothing to it. The IR takes a litle bit more consentration. The ir stuff in the cpl is very basic, but you spent 10 -15 hrs in the aircraft to learn it while when you do your IR first it will take you about half that time to learn it in the simulator.
I did my IR first because I did not have the hours required to start the cpl course.