At the moment Devour prioritizes allies over enemies when both targets are near to each other, although (in my opinion), it should be the other way around. The reason is, that you rarely have three stacks of Taste on an enemy (to have the ability to devour them) but teammates can be devoured at any time. This makes almost any situation in which you could devour an enemy a situation in which you WANT to devour it. When a friend is near though, the system curently prevents you from devouring the enemy and instead devours your teammate. This can have drastic changes on the outcome of a teamfight. This occurred to me multiple times already.
IMHO this is a must-change