I'm not the same caliber player as some of the others, but I can say I win Noble every time. The thing about Noble is that you're on parity with the AI, and the AI is terrible. Prince the AI gets an edge on you, which is scary, but it's very small, so you can still trounch them. All you really need to do to master Noble and Prince are the following:
1) Plan your cities well to maximize commerce and research
2) Specialize cities; in particular, so most of your cities max commerce but you have one or two early on maximizing production so you can defend yourself easily and roll over your neighbors if they annoy you.
3) Trade tech aggressively (In large multiplayer games, the tech trading metagame is probably the single most important part of the game, and the biggest determinant to winning past early rushing.)
Chopping aggressively is also a nice way to give yourself a massive advantage early on. If you chop aggressively and get out a few cities and improve them real quick, you'll be so far ahead of the AI in Noble that you're pretty much guaranteed to win.
But honestly, all of this is a bunch of nonsense. Really, if you just keep playing, you'll find Noble will get as easy as the previous levels are.