On saurfang I usually go berserker stance and use reckless ness about 7s before engage (boss mods have engage timers) and use bloodrage/shield block so i have enough rage to do a big shield slam crit to open with and because I blocked, revenge will light up and crit.
Other things could be that you dont heroic strike enough. Are you clicking? Are you keyboard turning? Hows your latency? Do you run with any rogues or hunters?
With regards to dying. Do you know the encounters well? Do you know when to use your defensive cooldowns appropriately? Are you getting external cooldowns from the healers? Are your healers doing something wrong?