Now, this might not be a popular suggestion, and I don't know how easy or difficult it might be to change, or even if I get the time of day reading this, but I think barrier champions should innately start off with the immune shield when they appear. They would work just like any other enemy that have a shield where it only regenerates if they haven't been damaged for a while and they can no longer regain health. A lot of times, people can negate barrier champions just by dealing enough damage rapidly so that they never activate their shields. The timed activation it currently uses also makes it difficult to use fragments like volatile and unraveling rounds, where I not only have to be concerned with keeping ads alive but I also have to time the activation of the buff with the shield. I know that radiant and intrinsic shield piercing weapons don't have this problem, but I like to make use of all my options when I have the chance. This would not only make you have to engage the barrier champion, but now you don't have to worry about the champion regenerating its health while you look for an enemy to kill so you can activate your piercing round fragment. This would also still work with radiant and piercing weapons as they can be used to just break the shield. Just something to consider in the future.