Being able to do your dummy "ideal" rotation is a prerequisite to be able to do good dps in raids. Try to understand your dummy rotation first, then when you practice in raids you should take note of the mechanics and phase changes where you can't follow that rotation anymore, and figure out how you should modify it to be ideal in that raid. Basically you're trying to come up with an ideal rotation for every fight, and you should aim to be as close to the dummy rotation as possible, since that's the "best" rotation you can do. The modifications may include holding buffs, holding geirskogul, popping buffs earlier, skipping some skills (phlebo, full thrust combo), while prioritizing heavy thrust, blood of the dragon and disembowel uptime.