Please don't use tier systems, its a very bad way to look on a Civ in my opinion.
China do have really serious advantages.
Better Generals, not only are Chinas Generals twice as good, the bonus all Chinas troops can get is pretty much imposible to get for any other Civ.
Chinas troops will all with some few exeptions be stronger then the troops from any other Civ.
Their is no way other Civs can make up for the stronger generals.
Promotions?, China can get them to and as well as any other civ with the exception of the Zulu.
Tech?, China can Tech as good as most civs and their military advantage could mean they get more cities and land = more people = more Techs.
Getting more generals is also very usefull and should not go unnoticed.
The Paper maker replace a building that you basicly get in every city anyway.
Its +3

advantage over the libary may not sound much, but what if you got 10 cities 20 cities even more for large empire this building can give you a 50+ gold for China, a very good and usefull building that really fits aggresive expansion play which the UA is made for.
The UU is very good for what it can do and its really improve the things it uppgrades to.