Not an ethical shot because there's so little margin for error. Might as well shoot em in the eye if you're going to take that shot (the target is about the same size).
I took one high angle shot like that once early on, and regretted it. It glanced off the shoulder blade and the arrow fell out. The deer was OK, but probably had a nasty pain in the shoulder for a few weeks. I learned my lesson right there: shots with a very narrow margin of error aren't worth it. Respect the deer and wait for a good shot IMO.