I’ve been working out regularly for almost two years now, and at this point I can leave myself sore–in a good way–with just about any workout. Except my back. While the rest of me can be sore for a few days, or even a week, after a serious workout, my lats and traps never really feel sore afterward. Is that normal for those muscles, or does this mean that I need to start working my back a lot harder?
And since I know someone will ask, my current back workout is four sets each of wide-grip chins, t-bar rows, and seated rows. I hit my traps on shoulder days with shrugs and upright rows.
You shouldn’t be using soreness levels as an indicator. However, I find that my back is sneaky when it comes to being sore. Sometimes I won’t feel a thing and then I will lean against something or stretch real good and all of the sudden I realize that it is pretty sore.
It was mentioned in the recent back article that many trainees use too much muscle when targeting their mid-back. Try taking the weight down and focusing on form (98% of people at my gym don’t row properly, bent over seated etc.). I’ve done this recently and I feel it a lot more than in the past. Also, make your training partner (if you have one) “coach” you on your movements. My brother and I train together and we constantly monitor each other, keep each other from cheating etc.
Actually, come to think of it, my brother and i are the only two people I have ever seen row without cheating.
Also, your arms may be pulling more than your back, I think there was an article on limb people or torso people and some exercises to help.
Are you progressing in terms of size and or strength with your back? If yes don’t worry about it, if no then worry about it.
People are probably going to flame me for this, but try doing some power cleans or power snatches. They’re easy and effective for recruiting HTMUs. I’m sure you’ll feel DOMS in your lats and traps quite a bit, and that’s all I’m saying. 
There is a breadth of scientific rationale behind this, but it’s worth reiterating the main point again: If your goal is simply to gain size then lack of DOMS is a non-issue. If strength or power are your goals, then your current training is not bringing you anywhere, but you probably know that already. Good luck.