This is one of the biggest things I notice.
It makes since that single-role medics should be superior to fire medics on a fairly consistent basis. It may be a regional thing, but this has not been my observation. I do know some great single-role medics, but I know far more who are terrible at their job with no desire to improve. And these aren't just guys waiting to get on FDs, either.
On the flip side, many of the best paramedics I know are fire medics. Hell, one of the systems around here that's known to consistently have stellar medics is a fire-based system. Even in my very large FD, where I will readily admit a good portion of our medics are sub-par in my eyes, I would still trust many of our fire medics over much of the area's stand-alone medics.
The idea makes sense. I like it. Doctors, or mid-levels, or nurses, or whatever area of healthcare you choose do not act as plumbers as another part of their job function. Theoretically, a single-role medic should be superior in medicine to a fire medic, since that is what they specialize in. In my personal experience, however, that is not the case. At least not with any reliable consistency.