I also agree that Dwarves are OP, but aside from early game, Angmar isn't really OP because the early units won't be effective if the battle draws out. Dark Rangers and Snow Trolls are good, and Angmar siege owns, but the WK is underpowered IMO and Rogash is always a HUGE target on the map.
For late-game, I think Mordor is OP and some might agree. If you've got the WK and both flying Nazgul you can take out most buildings in 1 swoop, or take out lightly protected fortresses in 3 swoops. You CAN use Nazgul against armies with archers -- just use WK and 1 Nazgul to swoop in, while the 3rd flies over and screeches. The archers will scatter and become fodder for Nazgul. Take out all archers first, then start smashing the infantry.
Mordor also has cheap (but inaccurate) siege, which use only 25CP, and if it's late game and you have 3 or 4 troll cages, you can pump out Attack Trolls quickly and wreck everything but heroes and pikes.
And last but not least, by late-game you should have a Lvl 10 Mouth of Sauron, who is deadly to both armies and heroes with Dissent and Evil Eye.