25 minutes? I don't think you're running intensely enough. I think 2.5 miles a day is great, but a lot of non-runners can probably finish in around the same time. Many of times I used to run in HS Wrestling, I would shoot for 2 miles in less than 17 minutes. That may sound like a drastic change, but in comparison to my little brother (who was a Cross Country runner at the time) he did 2 miles in 13 minutes or less. If you're running with good form, with decent shoes, and use it as a complimentary form of training, then you won't have to worry about joint problems (at least not as much as rolling hardcore as many times out of the week--depending on your training partners).
However, at 5'11" and 185lbs, I don't think you're too big or too small for your size. Now if you're looking at fighting competitively and you're shooting for the 170lbs weight class, I can see where you might be concerned. In which case, there isn't a hell of a lot you can do to shave off of your frame (especially if you have any sort of muscle mass). Going forward to that end, you're going to have to look a lot at what you're eating, as that will begin to determine a lot of factors in your weight.
I hope this did better to answer your initial question. I didn't read all the details until you re-iterated it.
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