Now that fates are buffed for xp, plenty of people run them as alternatives to leveling in dungeons, but the fate trains tend to only run in the zones already mentioned in this thread.

2.0 was the same way, with people running fates mostly in South Shroud, Eastern La Noscea, Coethas, Mor Dhona, and North Thanalan. The devs took note of this and added the Atma to the other 12 zones that people rarely fate farmed in. Only then did you start to see people running fates in other zones, as high level players grinded for relic weapons, enabling low level players to tag along on fates that couldn't be soloed.

I imagine you will see something similar added to the 3.0 zones soon, assuming the relic weapons are designed with the same intent of keeping content relevant at all levels.