Hi! Not as part of my experience in training, BUT as part of my professional experience, I am a post-graduated Nurse in Sports Rehab.
First of hall you will be adding stress/tension to that area, wich can be good or bad. There are a few things to consider first.
Here goes:
How is your posture?? Not just doing the exercises, but also during the daily activities? Some people do a slight arch on the upper back that causes the traps to be constantly activated/contracted leading to pain and massive muscular tonus.
Also check if your shoulders are rounding in as this could also lead to the previous arch on the back, and also shoulder problems (rotator cuffs mostly).
If you have any of this, you should adress your posture first!
Now as far as training goes, adding shrugs might actually help a lot. How?? Well just lift a light weight, do over 20 reps (assuming no pain when muscle warms), and after it aply heat and massage. You will benefit from the improved blood flow, and muscle tension will actually be lower a few minutes after the exercize.
If your traps are underdeveloped it is also a propblem with your training/exercise selection, review this, but remember, heavy loads should be placed only when you are recovered.
Hope this helps, i think i covered most possibilities.
(Sorry for my bad english, i am Portuguese.)