When you shift, all the parts of the derailleur pivot, and the cable slides in the housing too. I would attack it again with TriFlow, not only on the parallelogram pivot points but also the upper pivot that mounts into the frame, and the lower one that connects the pulley cage to the rest of the derailleur. If the derailleur's pulleys are bushing-type, take them apart and put a little TriFlow in them too. Lube the cable where it enters the housing, since some housings have little rubber o-ring seals in the ferrules, which can squeak under some conditions.
You might put a drop of TriFlow on the bottom-bracket cable guide too, if your bike routes the cables that way. If your bike uses a replacable derailleur hanger, you might try a drop of TriFlow between the frame and the hanger. Good luck!