Had a similar situation when I first did the Alysrazor fight on my Warrior. I'm a tank on him, I've never ever DPS'd as a warrior. I know to use inner rage when I reach 80 and spam heroic strike, but my rotation was crap, and my Raid leader informed me of it (During raid, however it was a similar situation on the other tank as well, so it wasn't calling anyone out) - I was only hitting up to 50k. Up until that moment I didn't realize I had any issue with DPS because to be honest I hadn't really worried about threat much on my tank - but then again I wasn't doing high teir raiding at that time =P

Long story short I hit the dummies, (which for a warrior tank I needed to pad 6k dps onto my numbers to account for lack of Vengance and Revenge (Revenge doesn't proc on a dummy...)) and started using Shield Slam every single chance I got. 2 weeks later I'm pushing 110k dps on that fight vs my old 50k (DPS Flasks/Potions/Trinkets help alot too!). The Raid Leader also informed me of an alternet spec which used Incite, which I didn't use ever, while I took his advice I changed it around a bit till I was comfortable and now we are constantly downing Alysrazor! ...now if that friggin' Flame Druid would just die @_@