Sire is one of the easier bosses in the raid.
Every single ability is on a fixed timer, there are no surprises in that fight.
The only thing that might kill you is hand of destruction together with soaking. If your heals don't top your group fast you might die there.
But hand has been nerfed. Even our casual guild killed him first try this week.
Shouldn't be a problem anymore for pugs.
I always wondered why hand is a heroic only ability. Hits pretty hard for that.