As Teng said, changing for those reasons is almost guaranteed to lead to very short term happiness at best. Unless you are ready to re-roll every other patch, you might want to find a better way.
For one, warlocks were at/near the bottom for quite some time. You never know when they will rotate right back there. For another, the odds are if you are feeling that far behind on dps, then the problem is more likely you or, loot luck. Changing toons won't fix loot luck.
The key is to find a rotation you like. If you like ele EXCEPT for the numbers, then you need to put in more work to get closer to your potential. Even when ret was near the bottom, I could consistently come in somewhere in the top half of the raid on dps with less gear. Those facerollers are not going to put in the work that you will. That being the case, you should be able to outperform them, at least at comparable gear levels. Sure, a frost dk may beat you from time to time with a mindless rotation. It's going to happen. It's just a part of this game. You should still be able to make him work for it to be above you if you are playing a class where you enjoy the rotation, however.
If you don't like the rotation even if you were happy with the dps, then you should find a class you like. Play an alt high enough to really get the rotation. Unfortunately, that may mean all the way into the 80s so that you see the effect of mastery. If you are kinda meh on the rotation, keep looking. Try another alt. It really will make the difference if you find the one you enjoy the most. Some of my favorite toons/specs have been underdogs on dps and I have ALWAYS been able to pull my weight with them. I played ret, unholy dk, fire mage and kitty dps when they all sucked and probably enjoyed them more then than at any other time. Getting good enough at them to make people comment on it (and sometimes inspiring them to roll one as an alt to try it out) when they weren't "supposed" to be able to do it has always been a guilty pleasure for me.
"he doens't need healing, he doesn't need healing, he doesn't nee-WHAOSHIT!wtf was that man!". Please stop leaning on TDR. -Teng