In STID, her abilities get overshadowed by the men in the film. She speaks Klingon, but nothing comes of it, and then there's a fight where she and her cohorts are saved by the "bad guy." That quickly moves on to a whole thing with him and Kirk, and to me, her "contribution" is easily forgotten.
You completely ignore that all our Starfleet heroes needed to be "saved" by Khan.
Then, when she beams down to "help" Spock, who's fighting Khan, again, her contribution falls flat to me. She has to rely on her boyfriend to take the bad guy out because he's more than her phaser can handle.
No. She put him in a position from where it was possible for him to overcome Khan.
You also ignore the fact that Dr. Marcus saved Dr. McCoy's life.