Sounds about right for me.
Dimming the screen will substantially improve battery life, but the CPU is a major major battery hog. So, CPU intensive apps like Flash are going to eat up your battery, kick the fans on, etc. The CPU gets hot because of the energy that goes through it to process information. If it's getting hot (and fans are blowing) it's chomping on your battery.
I can get 6-7 hours of light duty web browsing (no flash), word processing, etc. But any sort of video streaming always eats it up. I plug my MBP into my TV sometimes to watch content that Hulu doesn't allow to stream through my set top box. It can be at 100%, and after an hour long TV show, be down around 60% or even 50%, even though I could have gone 4 hours working on a paper or answering e-mails on the same amount of battery.
Still the best battery life of any laptop I've ever owned, and it's the reason I bought it. It accomplishes my goal, to leave the charger in one place. I am so sick of carrying a charger around all the time, unplugging my laptop, moving to another room, and plugging it back in; etc. My MBP, so far, accomplishes that. 95% of the time my charger doesn't leave my bedroom. I charge my MBP at night on my nightstand, or use the charger on my cinema display. Other than that, I can use it all day off and on and not need to charge it, or take the charger with me. That's why I bought this machine!
Also, if you use Parallels like I do, in coherence mode especially, that'll eat battery. Close parallels if you aren't actively using a windows app.
Turn your display brightness down (these displays are insanely bright, it's easy to run them turned down! Just try it and see if you don't realize it's dimmed down after a couple of minutes! I run mine at about 60%). Reducing the number of apps running in the background will help too.
It's true that the GPU will work a little harder in a retina MBP, but the batteries are bigger too to compensate. Apple had a little more room to work with by removing the optical drive, so they increased the size of the battery to ensure there wasn't a loss of battery life with the retina model (making it feel like a step backwards for some, like me, who would never consider a retina in the future if it had less battery life than the non-retina!)
