You've gone from 9th percentile to 50th...from far below average to an average raider...and you say you're regressing? That actually sounds like an accomplishment to me.

There is a phrase i learned in school to the effect of "the first 80% of something will be done in 20% of the time, the last 20% will take up the rest". Its easy to make the big strides to get something done, such as going from not using combos to using them, to using your buffs with your combos but the fine points in refining your rotation is what will take the time and dedication to perfect; its not something anyone develops quickly.

Keep trying and little by little you'll improve. It'll be hard, frustrating, aggravating and you'll have a lot of set backs but don't give up on it and you'll get there.