I have just finished playtesting this map as Good against the Fast AI as Evil and want to share my thoughts.
What I'm observing is essentially 4 fronts: The Gondor arena, the Orcs/Saruman arena, the Angmar arena, and the northern trio. Whichever side gets the upper hand the quickest in one of these arenas will usually win the game.
Rhun can take most of Northmen's valuable territories in a few rounds, partly due to their superior starting army and income, partly due to their superior navy.
Dwarves can help out, but they would need to send most of their resources to that front, which takes valueable pressure off of Angmar.
Woodland Realm will get pushed back and slowly overwhelmed by Dol Guldur since their income is comparatively low.
It seems that a good balance would be to give a small buff to the Northmen. Perhaps their army on the southern side of the River Running could be buffed to keep Rhun busy a turn or two longer. I also like your idea of giving the Northmen a little more production. I also think it wouldn't hurt to increase one or two northern Woodland Realm by one or two points.
Gondor's defense felt solid, but not invincible. I made the mistake of leaving 1/2 of my army out in the open to get smashed by Mordor. Fortunately, the AI did not utilize Harad well enough to take advantage of this.
I think the naval play between Gondor and Harad is a little underwhelming. By the time Harad buys enough boats to establish naval supremacy and transport a large enough force to threaten Gondor, enough time has passed for one of the other fronts to fall. Perhaps Harad can get a slightly larger navy to start out with, that way Gondor has to divert funds early on to counter that threat. Then again, Mordor can help out by sending their Nazgul, but that could undermine their land assault.
Not much to comment here. I think giving Angmar 2 dragons to start with is a good idea. It gives them enough projection of power without them being able to overwhelm Arnor early on.
In my game, the AI goofed up with the Orcs, taking Tharbad early on. This allowed Lorien to develop into a serious threat. However, Lorien will be quickly overwhelmed if Saruman and Orcs target them. Perhaps there should be more ents/huorns in Fangorn.
Only Rohan has proper seige units. Freefolk and High Elves do well enough on the plains, but they can't hope to take over any settlement unless they severely outnumber them. This is impossible to do against the Orcs since they have very cheap and spammable units. Moria can be held almost indefinitely even if Lorien and Freefolk send most of their resources to siege it.
One other thought. It seems like the game results in a stack contest in and around settlements which gets quite large. Perhaps there should be a roughly~20 unit limit for most territories and roughly ~30 unit limit for settlements/ fortified territories.
Please note that I'm not as good of a player as most here, particularly on this map, so some issues I see may just be due to my lack of skill. I hope this feedback helps.