Berserk puts me ahead of all the DPS in my group during A9S's opening. It's amazing to see.
You shouldn't be afraid of a 5 second pacification. Obviously you'll want to time it where you'll both get your 20 seconds of attacks in (three fell cleaves), but also not when you'll need to tank swap.

And if you're main tanking you have a lot more option to do it since you can use Deliverance to tank just fine.