dude, you suck?
Seriously though me and my 3 friends who have the game beat the first mission for both sides on gold on hard with no problems.
1-Knights are fine, you want them to become overpowerd IMO they do serious damage vrs sevral types of enemys and the other types get a bonus fighting them.
2-Armored works fine not seen any problem with it.
3-I agree with this the city AI is sorta lame sometimes they come out to fight heavy troops and die and then sit back while archers and range beats them up.
4&5- Archers are fine, if you give them more range they become broken, the idea is for you to keep them safe(btw archers can be 1 shoted by most knight units) Bows get unlimted assisting when your troops get attacked and there nearby, xbows get 1 attack.
6-All Air seem to a bit powerfull vrs ground units but at the same time they can be killed very fast with some range attacks.
7-Sounds like you didnt go far in the game, those scouts later do little damage vrs alot of the armored troops and can easly get 1-2 shoted by heavy hitters.
8- river crossings are fine, but i agree bridges should not give you the same neg.