I tried all sorts of thing you guys mentioned but still the same dilemma. Checked for cable friction, but that wasn't it, tried the middle sprocket adjustment, that didn't do it. Checked the hanger, seems straight(and the bike is new-ish). Also I find it hard to see any difference after playing with the B-screw, but I got it kind of close after a while. What I can see when I try to shift down is that the amount the RD moves from the largest to the second largest is about 1/2 or 1/3 as much as the rest of the jumps, so it's no surprise it doesn't drop. What could that be caused by?