I will agree that Orc Spam is decently hard to deal with, especially on the Rhun map because of the limited space. But from past experiences, one good thing about countering Orc Spam is the honestly the amount of Power Points you get from killing the orcs. Depending on what faction you are, you can get a Spellbook power that is really effective against orcs.
Every faction has some sort of way dealing with Orc spam. Archers and Cavalry, if used correctly, are incredibly effective against it.
I agree that orc spam is really the only way people play mordor, but I think that is the case because of how ineffective starting with anything else is.
I agree with the people that say Mountain Trolls need to be stronger. They are really only good against swordsmen. They also do good damage to buildings, but they are so easy to focus down. They become a lot better when upgraded, and drummer trolls are very useful, but I think how much damage they take from heroes and archers is the problem. I would suggest that they take less damage from both Heroes and Not Upgraded Arrows, and remove the ability for them to trample (because it is more of a problem then a benefit for Trolls because of how much health they lose from pikes), with a small price increase (maybe from 600 to 800). Also, maybe the Armour upgrade should make them slightly more resistant to all arrows, if it doesn't already.
Mollock has a lot of things that need some improvement, which is sad to say because of how good a troll hero could be. The best Example of this is Rogash in Rise of the Witch King. With only 3 abilities, he is able the best one of the best Mass Slayers in that game to do his High Damage, large AoE attack, High Armour, High Health, and extremely effective last 2 abilities. Now obviously I think making Mollock that good would be too much, but Mollock needs a lot of boosts to stats right now. He loses to cave troll lairs at level 1 if he is attacked first. That's a pretty serious problem.