Deadly Dog
Prince
I think of Yongle this way: you get 3 governor titles (researcher, connoisseur and tax collector) in every city that reaches size 10, so, eventually, all of them.Yongle is not game-breaking in the sense that every game is a foregone conclusion (he's vulnerable early), but he undeniably has an absurd advantage if he gets a few 10+ cities - it's just math. Science, culture AND 2 Gold per pop is simply too much of a bonus. He would be a pretty strong leader with one of those.
The projects are definitely useful when needed (pantheon, growing from 9-10, unlocking new district, etc).
Yongle doesn't compensate for a poor production start but adds massively to a really good start. Any city that deserves Temple of Artemis deserves it 10x more with Yongle.