Asking people to be cognizant of how far away they are is not rude at all. Personally, I think it's very rude when one party member stands themselves in BFE while everyone else is in proximity. This happens all the time in Void Ark. If you are the only person completely on the opposite end of the rest of the party, I'm sure not chasing you all over the arena to heal you. If you want heals, you stick with the group. If you want to sit in BFE, you take your chances on living or dying.