Coerthas Central Highlands has a pretty lengthy network of caves in the northeast, Wester Highlands had a few pockets, Middle La Noscea has a mine that exits out to Lower LN, technically parts of Southern Thanalan count as such, the pass from Vesper Bay leading to Cape Westwind is a cave, Dravanian Forelands has Mourn and a few other smaller areas within the mountain. . .

The caves and caverns are around, just rarely a relevant point of interest. Travel off the beaten path from time to time and go see what you can find