Interesting to look back on these results after 2 election cycles. The most 'Yes' voting electorate still in Coalition hands is the seat of Flinders, in 2016 it was the 12th most Yes-voting such seat
https://en.wikipedia.org/wiki/Australian_Marriage_Law_Postal_Survey#Result
seems even more impressive when looked at using 2016 margins where the coalition gets 60-70% 2pp vote in most of these seats
note Warringah at 10th place with 75% support