Chaff is really only effective if you notch. Volume of chaff makes no difference, as you demonstrated. Chaff is not a magic, make the missile miss, button. It really only works if you turn and fly 90 degrees tangent to the face of the Radar (missile or plane firing depending on the missile), and drop 2 or 3 chaff as you approach the 90. The R-77 will lose you and go for the chaff if you're flying 90 degrees to the missile, then you can re-engage. Tangent to the face of the missile or radar emitter means any direction, by the way... could be turn right 90 degrees, could be aim for the deck... any orientation that puts your velocity vector a 90 degree tangent to the plane of the radar face.
Typically, at least a shallow dive helps in notching, because then you also have background (ground clutter) working in your favor too.