Most of what I'm going to say has already been said but I'll say it again anyways. Please take what I say with a grain fo salt because I've played Mordor twice in my entire SBG experience and both times were back in '04.
First; Orcs with Bows(Unless Volleying and even then) = opponent go
Drop them for more shield/spear orcs and form a giant wave.
Second; Consider trading out Orcs with Two-Hand Weapons for Mordor Uruks with two-hand weapons. This would give you some heavier hitters without having models that scream "shoot-me-I'm-gonna-kill-you".
Third; I don't know how you feel about allying troops in, but I would consider allying Easterling Pikemen with a Captain instead of the Orc Bowmen, Orcs with 2-hand weapons and one of the Orc Captains. This would allow you to form a phalanx which you could use to grind down your opponent.
Fourth; Take a Ringwraith, preferably the Shadow Lord on foot. Put him in the center of a large block of Orcs or the center of the phalanx I suggested earlier and now those s2 and s3 bows are basically null and void so long as the Shadow Lord is near. In terms of Ringwraiths Khamul and the Undying are the next best IMO, though I will admit I have limited experience with Ringwraiths in SBG.
Fifth; I have no experience either with or against Shamans of any kind so I'd avoid using them.
Sixth; Trolls..... Not sure what to do with them. I'm tempted to drop them to help pay for the Ringwraiths but I've never seen two fielded in one army list so I am intrigued at the possibility.
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