I never paid much attention while leveling, but you obviously get better resources from each shipment as you get higher. Is this based on your rank, or on your hourly production?

It's rank-based. You'll notice there's a bell curve over the different minerals. As you rank up, the "center" of the curve (the mineral you get the most of) will gradually shift toward better minerals. Which in turn means the "slopes" shift as well.

yeah ive seen that, wasnt sure if it was from ranks or increased production though, as they've gone up steadily at equivalent rates.

Also at rank 85 you begin to receive Kurenite on a regular basis, and at 160 you begin to receive Aidonium on a regular basis.