Yes, that IS very important. The last thing you want to see when you join a raid is a def up on a boss that's not supposed to have it x.x
The demons buff themselves, too. Ult demon's normal OD is atk buff, raging OD is random 10 hits - you don't want the atk buff on a random 10 hit if you can help it. But it sounds like you're well prepared =)