I've brought this up a few times and I guess I'll just keep doing it
From a climatological point of view the worlds we're dealing with are uncomfortable to look at. Temperate forest and desert seem to be the overwhelming 'default' terrain, established along a gradient of aridness and large median temperature ranges that totally rule out any transitional terrain between them.
Arid shrubland, which is specifically supposed to be 'desert-lite,' is generated only by high temperatures with no regard to aridness, so you'll often have arid shrubland getting 1500mm precipitation/yr and sitting right next to jungle.
It would be nice to play arid shrubland with milder winters, like we do on much harsher desert tiles. If it were to operate as a 'buffer' terrain, between dry and wet terrains, it should have a low yearly precipitation (500? 550?) and winter temperatures high enough to distinguish it from tundra.