I am on my home screen for a few seconds when switching apps but when I am watching a video, it is sometimes for hours at a time. Your argument would be valid if the live wallpaper was sucking battery when it is in the background of if you spent tons of time on the home pages, but that isn't the case.
On MX, I have transferred home videos from a digital video camera and I have transferred MKV files and they are all jumpy using HW mode. If I use handbreak to convert them, it is just fine, but that is a real pita. DICE just seems to work better for me, but to each his own.