Originally Posted by Ello

Is yours an assumption, experince or really proven?

And that's the problem, we don't know the droprates for gold dragons (or Manyus for that matter), we don't even know whether there is actually any variety in those rates between the different maps.
And with FKG, I wouldn't blindly assume that more stamina=better. Just look at the intermediate Secret Garden or daily gold maps, which aren't as efficient as the beginner maps. Or 13-X not being as efficient as 12-3 or 12-5. The rewards actually don't seem to be very important when the developers design these maps. They seem more interested in creating a puzzle-aspect and making the maps somewhat fun to do. Difficulty is mostly decided by the level of the pests, and the potential rewards scale with that. Avarage or minimal rewards hardly seem to be taken into consideration at all, only potential maximum rewards.