You can' t take two deer at once with confidence because you don' t know how an arrow is going to act coming out of the first deer. Even if you have both animals lined up perfectly, how do you KNOW the arrow isn' t going to deflect on a bone on the first animal and gutshot the next one? How do you KNOW the broadhead won' t get damaged on the first deer and be in just good enough shape to wound the next one?

Don' t even think about it.