Hmmm--I almost never play that game for that long at a time. I'll try to remember to take a look next time I play something else that I'm going to be playing for at least an hour.
I did take a look at my battery stats just now after another session of Dawn of Titans. In my 7-day stats, it says I've had the game on screen for 2.6 hours and it's used 17% of my battery in that time. That's pretty great for a game with that level of graphics quality. So that's about 10% an hour, which is about what I expect to get out of any app. Usually games drain faster than that, but this one doesn't seem to. It is a newer game and was launched post-Metal. The great thing about my 10.5" Pro has been that the regular non-gaming apps have been draining my battery much SLOWER than 10% an hour, which is why I'm getting so much more usage out of a single charge. I don't know if it has to do with the iPads ability to vary the refresh rate or what, but it's pretty incredible.