First of all, what was said in this thread is right. Less reps are for building muscles. And it makes a big difference. But what is a low amount of reps? It's everything below 15 or 20 actually! It doesn't make too much of a difference if you do 8 or 12 reps, both is a low number and aims for building muscles. In fact you should change your reps and sets anyway, so there is no best number. If you want to build up muscles, you'll do 8 reps once and maybe 12 or 15 the other day while changing the numbers of sets,time of rest, weights. But all that this is still for building up muscles - if you go to your limit, of course.
And so, since you don't wanna do that, I'd change the routine anyway and aim for maybe 25 reps per set (or even a lil more), maybe 2 sets per exercise. Maybe you could do a cycle training - do about 8 or 10 exercises for different bodyparts in one run without too much rest..... after you finished, take a rest and go for a second run and then your done. You shouldn't feel like your wasting time then.