Is the quality of a ii chord in a major scale minor?

The quality of any lower-case chord is fundamentally minor. ii chords are useful in chorales, where in most cases, the final cadence finishes on a ii7b V7 I chord sequence in a major key. While in its purest form, a minor key signature makes the final cadence trickier, most of Bach's minor key chorales are written with a Tierce de Picardie - that is, finishing on a major chord in a minor key - though this would not affect the finishing cadence, as the only present sharpened note in the finished cadence would be the major seventh.