It does sound like something is experiencing stiction. Starting at the top,it could be the cable. How old is it? If you disconnect both ends, how hard is it to move?
Then there is the arm at the bottom end of the cable that transfers the cable motion to the clutch push rod that runs through the transmission. The arm has bearings that get loaded up with dirt and become very hard to move. It's in a spot where a lot of road dirt and water get thrown on it, yet it is almost impossible to clean. This is where I suspect your problem is. There is info here on cleaning it. Some of us have drilled it out and installed a grease fitting to help keep it lubricated.
The pushrod may be bent, but that would make it hard to activate all the time, so I doubt that is your problem.
Last is the clutch splines. These need to be lubed, but make it difficult to fully release the clutch, making downshifts very difficult. I am not that sure that lubing them will reduce the resistance in the lever pull.
Bottom line, go after the clutch arm behind the transmission.