Fair point, though i think you're on to something in that Khan was laboring under Marcus for long enough that he became an individual driven by rage. I love the fact that Marcus is the real villain, only to be usurped by his own creation-sort of, obviously. But, the idea that he thought he had Khan under control only for Khan to kill him was a nice twist that I liked. It also demonstrated exactly what Khan was capable of, which was murder with his own hands.Khan in his prime was Montalban in "Space Seed" for me. Yes, in Into Darkness it was cool to see Khan unload, even if it was a bit overdone. That being said, Cumberbatch's cold fury never jibed with Montalban's take on Khan IMO. Montalban was more charismatic. Montalban was more likable. He was a seducer. I can't see Cumberbatch's Khan seducing Lt. McGivers for example.
Granted one could argue that Cumberkhan was reacting to his treatment by Admiral Marcus whereas Montalban's Khan awoke in a different situation and used different tactics. But still it didn't work for me. I did like the Kirk-Khan team up, that wasn't expected. I also liked how Admiral Marcus was the real villain, though I just thought about it, did that diminish Khan further that he wasn't the main villain in his ''own" film?
To answer your question, no I don't think either villain is diminished by having the other. I think it shows the great lengths both men will go to achieve their goals, and their own breaking points. To me, they reflect off of each other.
See, I think Khan was far more his own character, separated from his support system, and slowly going insane from fury and revenge. I don't think they were trying for "Space Seed" Khan or "TWOK" Khan, so much as they were trying to tell another Khan story in different circumstances.I also felt that they were trying to have both "Space Seed" and "TWOK" Khan all in one in Cumberbatch's performance so it was a much shorter window to see the devolution of Khan's character than we got with Montalban. In any event, I thought Malik from Enterprise's Augment arc was a better homage to Khan than what we got in Into Darkness.
I didn't have a problem with the Klingons. If nothing else, I think there is more to develop from them, and see what their capabilities are. We never saw a bevy of ships attack the Enterprise in any TOS movies either.And to keep this on the Klingons. I liked the Into Darkness look for them, from foreheads to clothing. I didn't care for the ships. They were too ramshackle, for lack of a better word. I also don't think they were badass enough. No way Kirk and crew should've made it to Qo'noS so easily, and also how could the Enterprise be on the edge of Klingon space without a bevy of Birds-of-Prey or battle cruisers encircling them? To me Into Darkness made the Klingons too weak. Into Darkness Klingons were no comparison to any Klingons in the TOS films.