a lot of factors come into play....what rear end diff does it have? 6 speed automatic? Where you live and terrain play into it as well. I live on the prairies, so pretty flat land and I also use mine as a daily driver...I can hit 13-14 pretty consistently, will drop some in winter time...when pulling out 5th 8-10 is more the norm depending on wind conditions. Best I ever got was 11.5 with a tail wind.
But as far as power goes, I am quite happy with it.
2011 GMC Sierra 2500HD
2014 Rockwood 8289WS, Diamond Pkg.