It could be the cables and housing, it could be as simple as adjustment of derailleurs. As stated above, I am not mechanically inclined, but I have learned to all the work on my bikes myself. At first, still sometimes with help from a forum, or videos, like youtube and Parktool.com. Does the bike have internal cabling?

Another thing that helped: I switched to a Ritchey Beacon drop bar, extreme shallow drop and short reach, that changed the angle of the STI levers, which straightened the cable/housing where it exits the levers. I really believe that did a lot of good for the shifting. And, I really like the handlebar.