Odina you got sth wrong there.
Banner has to be cast prior to Dragon Roar for 20% crit damage boost. Same goes for Berserker Rage to make sure that you are enraged. What you are talking about is Recklessness.Throw down a war banner at your feet that increases the critical damage of party or raid members within 40 yards of the banner by 20%. Lasts 10 sec.
If you cast banner after DR you miss out on 20% damage and 20% of that damage is not applied to Bloodbath aswell. Not good.