I just failed The Final Day fight TWICE because two different people disconnected midfight. Meaning we didn't have an LB3, meaning we died. Mandatory LB3 doesn't actually add anything to gameplay. It's a glorified Press X To Win Game quicktime event. All such a mechanic brings to the table is the ability to have the fight ruined by garbage netcode.
LB3 was always one final burst of damage to finish off a fight, or a healer's saving throw after everything went pear-shaped. And tank LB was always totally irrelevant. And that WORKED. Then they came along and fixed what wasn't broken by forcing Tank LB3, and now it's actually broken. Good job.