I wouldn't unload my quiver into a spine shot deer, but I would put 1 more arrow thru the lungs, thats all it would take to kill it!
You're missing the point. Rarely (as in never.....in my circumstances) will you have an unencumbered, "sure-thing" shot at the vitals. In this case.....I feel like it's MORE ethical to throw caution to the wind and shoot anyways. A vitals follow up is "ideal" but ANY arrow hitting the deer is better than one NOT sent.