For the axial tilt, you've mentioned temperate seasons and you've mentioned wet/dry seasons, but not what causes the wet/dry.

Monsoons. There is this thing called the Intertropical Convergence Zone - that point of the earth's circumference where at any given time the direction to the sun is exactly perpendicular to the earth. Because air is warmest at this point it rises more strongly and cooler air from elsewhere on the planet moves toward this zone as a consequence, bringing humidity (rain) along with it.

On a planet with an axial tilt, this happens at the equator exactly twice a year on the equinoxes, bringing the greatest amount of rain and giving rise to mostly tropical rainforest. By comparison, the tropics of Cancer and Capricorn get this only once a year during their respective summer solstice. The upshot of this is that the tropics exhibit deserts that rely upon the monsoon during high summer to bring much-needed rain and plants have adapted to cope with just an annual drink.

When I look at Thanalan, I see such a desert with the sort of vegetation that subsists off either the rare rain events or other sources of groundwater, which would place it on a tropic.
Mor Dhona, Vylbrand and the Black Shroud have characteristically temperate environments. Mor Dhona appears to be a temperate rainforest based on the amount of river water fed to it from both the north and east and prevailing weather patterns from the west.

This means the planet's equator is off the southern coast of Thanalan and Eorzea is, by its own frame of reference, in the northern hemisphere.

((PS: I admit this theory is incomplete and has the odd hole in it.))