Medivh corrupted by Fel, oh please, he WAS Sargeras and Medivh and Guardian, why did he even let orcs in Azeroth, of coarse because Aegewynn sealed Sargeras tomb "so nothing from this world" could open it, and Sargeras found loophole to get his avatar body back... and like such Fel could corrupt Medivh the Guardian, he was such a noob in movie. And there was no redeption for Medivh.. opening portal to SW.. lols, after Khatgar, Lothar and Garona killed him with help of Medivh human part of himself, his mother resurrected him, remember? He went back to Karazhan and took back Guardians power and responsibility, he was just Medivh the Guardian, without Sargeras... he was the good one for the first time in his life.
No mention about Garonas curse, so warlock can control her, she killed king, but she was just a tool in warlocks hands against her own will... and that fueled war between orcs and Alliance even more, that is very important aspect of the plot.
Explanation how Thrall became green was epic tough, loved it.