It does have a pretty strong recoil spring. The trigger's main spring doesn't strike me as being particularly heavy.
Hey, let's have an experiment. See how hard it is to pull your slide back with the hammer up. Then do it again with the hammer cocked. Of course the slide will be easier with the hammer cocked, but you'll get a feel for the difference. Then, take the recoil spring off the barrel and put the slide back on, and pull the slide back with the hammer up and with the hammer cocked. Naturally, with the hammer cocked and no recoil spring you'll feel only the resistence of oiled parts moving with one another, and it should be pretty effortless. If it isn't, you should sort out any friction or mechanical problems as you find them.
My hunch is that the springs are just stiffer than you expect.
Scott