Thanks all - there is some really good advice here throughout all of these posts. I think we're leaning towards staying with the same plan:

2 nights Melbourne (get over jetlag, maybe at about-to-open Ritz)
3 nights Saffire Freycinet (potentially split with 2 nights Saffire, 2 nights Pumphouse Point, and then shorten Sydney by 1 night)
3 nights Sydney (Park Hyatt)
3 nights Lord Howe (Capella)

I need a couple of nights in a city to get over jetlag - Melbourne fits that bill. I'd regret not seeing Sydney given I've never been to Australia. Furthermore, shortening MEL/SYD further doesn't give us enough time to add another nature-oriented destination. GBR would have been a good add (probably Lizard Island), but the travel is way too complicated and too overlapping with Lord Howe Island.

With the above itinerary, we can fly on only non-stop flights for the whole trip (besides transpac) and the flight times are fantastic.

Thanks again, everyone.