Try pumping the clutch rapidly. Does it engage further up? Is there any evidence of leakage at the master or slave?
It sounds like you have bled it, but if multiple bleedings don't work and there appears to be no entrained air, it's probably one of the cylinders. The slave is usually the first to go, so if you replace or rebuild it and the problem persistes, rebuild or replace the master.
Bienniel fluid flushes, along with the brakes, will prolong the life of the hydraulic components, but, unlike the brake cup rubbers which move very little, the clutch system cup rubbers see full stroke every time you declutch and wear. That's why you get all the black crud when you flush the fluid.