What Sequoia are you looking at? Mine has a rear diff locker. 2010 Platinum. All the 2nd gens I looked at had rear diff lockers.
The Sequoia has been great to me. It's like a bigger version of my 4runner with more amenities/features and the captains chair is so freaking comfortable.
I have to say, the air conditioned seats is one of the most amazing things I've ever experienced- I'm 6'1" 225 and run hot all the time, that shit rocks!
I get 15 MPG average and we do a lot of city driving with it. 20 Highway 13 city. Not too bad for it's class and power/size combo. It can haul a big load too. just under 10K.
For a vehicle in that size/class you typically sacrifice power/torque for higher MPG, so I guess it depends on what you are going for.
Try the Lincoln Navigator with twin turbo V6. It checks off everything on your list I believe, the rear diff lock maybe not, I forget, that was a while ago I looked at them- and I think it is 17/23 MPG. One of the only vehicles that size other than the Sequoia that is BOF.
The V6 Twin Turbo was robust, but didn't have the torque or HP, acceleration or mountain performance that the 5.7L V8 does.
I test drove a few, but the Sequoia blew it out of the water in every sense for me, I don't care about MPG's all that much though.