1. Temperate is treated as being richer land than Mediterranean, which seems backwards to me. I can accept this as a balancing factor designed to boost the Gallic tribes relative to the Romans, if that is in fact the intent. If realism is the intent, then reversing the modifiers (no modifier for Temperate, +10% tax value for Mediterranean) should be more accurate.
2. I'm not convinced that the Fertile Crescent and Mesopotamian provinces are correct to be assigned Semi-Arid. That's about right for that region today, but had they already been that badly damaged 2300 years ago? If not, Mediterranean would probably be appropriate (certainly for 5-6000 years ago; perhaps a middle ground of a no-modifier version of Temperate as in point 1 would work for this time period?). Damascus, Susa, and Persepolis being Arid seems odd as well. All three were hugely important cities during or very shortly before this era, so it seems strange that they'd be in what amount to desert provinces. If Arid is actually correct for those regions in this time period, perhaps an even more extreme "Desert" climate tag should be added to differentiate these cities from places like Libya province?
3. Some provinces are simply wrong. Gallia Cisalpina (capital: Milan) is assigned Highland climate, presumably because the province includes part of the Alps. The province also includes a hefty chunk of the highly valuable and productive Po valley, so one of Temperate or Mediterranean would be correct (wikipedia says Temperate for North Italy's inland plains like this). The same logic in reverse indicates that Helvetii should be Highland not Temperate. IIRC, Caesar noted that it was a poor land whose inhabitants tried and failed to take better land in Gaul in the Gallic Wars. And really, if the heart of modern Switzerland isn't Highland, what is?
Ditto for parts of Armenia - there have to be Highland provinces in there though I don't know the region well enough to say which ones for certain. Again I believe it was Caesar who remarked on the extreme harshness of the terrain, and Continental doesn't do justice to that.
Just checked, Pictii is also currently Temperate not Highland.