I raided all through Wrath, and in 3.3.5a, Enhance DPS was rocking. I was pulling 11-14k, depending on the boss, and typically in the top 5 dps in 25m raids. I don't yet know enough about Molten to know if certain functions destroy Enhance DPS, but in retail, only during TOC days did I feel Enhance was poor. Also, they make up in buffs what they lack in raw power, and Purge spam helps so much vs. Faction Chumps. Enhancement's priority (not rotation) is what most people have a difficult time with, and any small mistake can significantly destroy your dps. My guild once tried to replace me with a better geared enhance sham (he had better weapons and BiS trinkets) and I still out dps'ed him by 2k. Enhancement is just very difficult to balance, stats-wise, and has a much more complicated dps priority than other classes.
http://wow.joystiq.com/2010/05/06/ic...lysis-by-spec/
Here's some data collected during ICC that shows average DPS of classes, and Enhancement is almost right smack-dab in the middle. "One of the lowest" is only true by technicality, as anything that isn't the best is "one of the lowest".
With respect, your statement is just absolutely untrue. Also, what Enhance lacks in raw power, they more than make up for in buffs, interrupting, purging and the always useful Bloodlust/Heroism, and there's no reason not to have just one in your 25m raids (10m is debatable).
Edit: Forgot to mention Windfury Totem > Imp Icy Talons as well, as a Frost DK can get more DPS by relying on WF totem for that buff, and speccing elsewhere.