Lwaxana was in... four episodes of DS9 I think it was and their success was questionable. So you wanted just one more Q episode?
Q's at his best when he's the cynical superior lifeform with witty taunts more than just playing an almost Joker like role. DS9 featured only the latter, Voyager did two out of three episodes and TNG was hit and miss with him two as there were some cringeworthy episodes like Hide and Q there too.
De Lancie just delivers with such style, that even the bad episodes he stars in can often be forgiven.