Which brings us to the point that FXS still don’t fully realize, or don’t want to accept:
Bad tiles are still inherently bad tiles. Giving civs decent bonuses for those tiles isn’t a real advantage, you are merely evening out the playground. A civ still needs food and production, something these bad tiles cannot provide - which is why you end up with “tundra/desert on the edges” kind of strategies. Also, the border expansion logic avoids these tiles like a plague. Even if you have Petra, the game will consider desert tiles as low priority, because it doesn’t consider the added bonus of Petra when choosing the next tile for expansion.
For this same reason, I am still extremely skeptical about the Inca. No, just because you can work mountains doesn’t mean you will have better yields than other civs.
No, FXS's problem is they have never correctly modeled the amount of variation and enhancement that humans have done to the terrain around them. 'Bad tiles are inherently bad tiles' only in the game, not in the historical record:
The central California desert, with Industrial Era and later irrigation and bio-engineering, have become the most productive agricultural acreage on the planet. Operative Word Desert.
The Inca could create farmland by terracing mountains, plant an early example of genetic engineering (potatoes) and extract more calories per acre than anywhere in Europe could with traditional 'flatland' agriculture.
Native Americans managed forests in eastern north America for both agriculture and game, produced man-made fertile soil for rainforest garden agriculture in the rain forest, and planted about 1/3 of the Amazon rainforest to get plants that were useful to themselves.
As long as the game doesn't allow us to replicate historical human civilizations' abilities, 'Bad tiles are inherently bad tiles' and the game is sadly lacking in opportunities.
As to the debate over Mali's pluses and minuses:
Early Production now is dependent on a decent Start position, with productive tiles. IF Mali has a Start Bias for desert that is actually coded correctly, they will get Gold early regardless of whether their neighbors have Production. In my experience, I buy something early in the game every single game with Gold to supplement lagging early Production. Instead of 1 unit or 1 building in the first 20 turns, Mali will be buying 2 or 3. I think people will find that they are not much disadvantaged at all.
Deserts are second only to Tundra in spawning Barb Camps, in my experience (and I've played on Hot Arid maps with lots of desert, and the little red buggers swarm out of the sands like Locusts). Given any chance at all, Mali can go Barb Hunting and supplement his Gold even more: on a standard game, 2 Barb Camps and ordinary production will get you a Slinger or Scout, 3 will get you a Warrior 4 will pretty nearly buy you a Granary or Monument. And that's without the +4 Gold from a Mine Mali gets...
Let's see, add to that safe trade routes across those deserts with the Mandekalu, cheap CH, Massive amounts of Faith from desert cities that, with a Monumentality Golden Age allow you to Flood the Map with Faith Bought Settlers/Builders: I predict that the 'negatives' for this Civ will only apply to those who are Fixated on Production to the exclusion of all else...
Myself, I plan to name my first Malian pure desert city Tanais and wait for an Archeologist wearing a fedora and carrying a bullwhip to show up...