[Eldar14]

Of course, and army of orcs and and army of trolls are of two completely different sizes. It takes a lot less trolls to be considered an army, and I'll assume this armies are as small as they can be and still be considered an army.

Now that my 'army-size introduction' is over, I'll say what I think will happen. Once a group of orcs is an army, a 'somewhat leader' would be an actual leader who just isn't very good. Once you factor in that the Uluk-hai fighting, I'll assume the leader is at least somewhat skilled in battle tactics. He would probably get his men to the high ground, and try to do some damage with arrows (even with thick skin, there are weak points, ex. eyes, mouth, etc. Also, some orcs could probably draw a pretty big bow, so these arrows could be big enough to pierce troll hide) Then the Olok-hai would charge, smashing into the Uluk-hai. The initial blast would make the line start to fall back, but the Uluk-hai are good enough soldiers not to retreat. They'll form some sort of defensive formation, and use some sort of lance-like weapon to halt any Olok-Hai who try to do a full scale charge again. This line would slowly advance while the 'leader' attempts a flanking maneuver, which would take out a few trolls before it is destroyed. The destraction, however, would allow for a charge from the Uluk-Hai, which might force the Olok-Hai into a retreat, or at least do enough damage to turn the tide of the battle, almost assuring the Uluk-Hais' victory. That's my theory.