don't forget that marines and tanks got nerfed into the ground. marines lost 2 damage and tanks lost like 10. high templar and archons got many buffs and zerg players stopped thinking infestors were worthless (Destiny popularized them in the same way that whitera popularized warp prisms). In the beta they were only used for very specific cheeze strats

I'm just gonna point out that the OP obviously didn't follow the scene closely. Terran was considered OP largely because of the Korean scene. The original SC2 Terran was grossly broken and was nerfed many many times before it even got to the point the Terran was not dominating the scene. Protoss and Zerg recieved many buffs during that time as well.

Terran was OP bio-ball was absolutely godly, and destroyed everything. Also it was easy as hell to micro for how effective it was. It wasn't unbeatable but for the other races to win they had to completely outplay the terran. There was a reason it got nerfed so many times since the game came out.

edit: I don't think Darius is OP though

Darius isn't OP, but it's really hard to not be annoyed as hell when he's in the match.