Okay so lets start with Durotan, 'cause he's the only one whos both likable and with a consistent character:
He's all proud and noble and thinks its beneath OrCs to enslave women and children and sacrifice old people for Fel Magic. He's the only one who considers humans worthy foes and doesn't trust the Fel Magic.
And to protect his wife, newborn child and his tribe he tried to form an alliance with the Humans to kill Gul'Dan who he believes is not only responsible for the OrCs world being destroyed, but is destroying the human world too. And his pal, Orgrim, betrays him because he wants Fel Magic. They imprison Durotan, kill his entire clan, and Orgrim in a moment of I guess guilt lets the wife/child go, but the wife gets killed in the next scene so its kinda' moot. Orgrim them, in a complete reversal of his betrayal, lets Durotan out of jail so he can challenge Gul'Dan to single combat in the hopes of showing the entire Horde the demon magic that is Fel. Gul then uses his black magic to kill Durotan in the duel, to which Orgrim and Blackhand say was un-OrCy and dishonorable and the clans start to turn against Gul.
Gul then tuns Blackhand into like an OrC/Plant/Demon hybrid who roars alot and kills some orks. Gul also kills a few rebellious Orcs, and Orgrim and the horde basically fall into line again, rendering Durotan's entire sacrifice meaningless.
Gul'Dan: He's evil and corrupt and enjoys torturing humans and doesn't tolerate failure or any other OrC talking against him. He's almost comically demons and cruel and the OrCs just seem to let it slide. Even after he basically hollows Durotan out and uses his life-force to turn Blackhand into a rampaging monster, the OrCs are surprisingly chill about it.
Orgrim: He's a plot device. A means to an end. The cause of Durotan's imprisonment, and his eventual escape.
BlackHand: He had the potential to be complex, but he gets turned into the weird demon plant thing so its moot. He was all 'Kill the humans!' and the like, until he gets his hand blown off by a 'Boom Stick' and then he starts treating humans with more caution and respect. And when Gul'Dan is loosing the fight with Durotan and asks for his weapons back so he can finish thing quickly, BlackHand is all "No true OrC runs from the Amok Time" and refuses. And then he gets turned into a monster. And then fights the human dude, Lothar, and gets stabbed in the dick and dies.
So by the end of the movie Durotan, his wife, his tribe and Blackhand are all dead, Gul'Dan has enslaved the Horde and Orgrim is off being a mopey slave.
Oh, and Durotan's son is now mosses. Literally. The mom, in a completely desperately poorly written scene, puts her dagger on the shore, puts the baby in a basket, wades into the water, says something about honor and nobility and warchiefs, and sets the baby in the water to float away. She is then stabbed by her own dagger and dies.
