I have an 11 Yukon Denali. Pretty similar to what you are talking about.
While I don't feel like the rig is under powered, I don't think it feels like 400 + HP.
My complaints on mine is it runs hotter than I think it should as a tow vehicle (swapping to a bigger tranny cooler next week). It has more rattles than any vehicle that I have owned (other than a 2500 Burb I bought with 120k on the clock). Interior does not compare to the top trim levels of similar year Ford or RAM. And I have had ongoing issues with the Stabilitrack - have had wheel sensors go out twice where it shuts the stability control off, and am experiencing similar problems again.
When I was looking for this vehicle 3 - 4 years ago, I found TONS of Burbs/Yukons for sale with 200,000 plus miles. So they do seem to stay on the road forever - and they hold their value well.