So, one final thought on these vinyl adventures is a query. When I first looked at them, I was struck by how strongly the character Mercion, the cleric, reminded me of Elmore's drawing of Aleena the cleric in the 4th edition (Red Box). Both date from about the same time (1983 for Elmore, 1984 for the vinyl). I think the image stuck in my mind all these years because it's rare to kill off competent, likable characters. Since the Red Box image is readily available but the vinyl adventure difficult to come by, I've attached a few of the relevant images for comparison.
It was before my time (I didn't arrive at TSR until 1991), but maybe the creative team at TSR in 1983 disliked Lidda, Mialee, Regdar, and the rest as much as the WotC/TSR team at the time of 3e's creation disliked the official iconic characters foisted upon them. Certainly (to cite one parallel) there was residual disdain for the D&D cartoon characters lingering on years after that unfortunate episode in TSR history had faded into the past.