My '12 Denali XL had very slight rough idle in drive. Enough to feel it when sitting at traffic lights, but it was not continuous. It would happen randomly every so often, but was unquestionably there.
I changed the oil, which was PURE BLACK (not sure how many times it was changed!), put in 2 bottles of Techron, and drove it 300+ miles to let the new oil and the Techron do its work.
The truck idles so smoothly now that sometimes when I'm sitting at traffic lights, I completely forget my truck is on and think it has died on me or something. It is really that smooth now.
Of course, every now and then, I still feel a slight vibration from the powertrain. It's important to note that our powertrains are supposed to have
some type of roughness to its idle; that's what I gleaned from hours and hours of research on many different forums as well.