You walk into an encounter not understanding it, you should either adjust on the fly and beat it, or wipe and try again with better understanding. I'm not being arrogant at all.
Raid boss debuff applies to someone, nobody knows what it does. They let it expire and it blows up half the raid and they wipe. Next pull they know to move out of the raid for the expiration and kill the boss easily.
This happened to me last night. First attempt: wipe. Second attempt: win! And we all became better and smarter players for it.