I was just as surprised as you are. The laptop got uncomfortably hot as well. I was very disappointed and had to purchase an inverter on the road to use my adapter.
My 15 dies somewhere between 3 and 4 hours (Java/C++ dev) and the lack of battery capacity is very noticeable (previous 15 with nVidia ran for about 5 hours)
I'd bet that this same program eats the battery of any Mac, hence it being a Civ issue, not a Mac issue.
Call me on this if I'm wrong.