The Immortal has been the meta in every single game of Iron Banner I've played so far since it dropped. I've done all 12 challenges across all 3 of my characters, and have gilded my Iron Lord Title. There should be a reward, like an adept weapon, specifically for Iron Banner, to even the odds against Trials players with their adept Immortals.
Edit: I just want to emphasize that I have no issue with Trials players using strong weapons, everyone has their thing and the meta changes regularly. But if a weapon is brought it that only some people are capable of getting, and it becomes an instant game changer, like the immortal, then the rest of us should have access to something equally as good, and IB is a good method of delivery.
2nd Edit: Yes I'm aware I "could go flawless" except that's not an available option for me. I'm not awful at pvp but I'm by no means trials flawless level. Hence suggesting an alternative method, other than waiting for GM's