These are the results of simulationcraft, in best in slot HC gear. Have to take next in mind when analysing that data:

- this is single target
- simulationcraft relies on the community to keep the profiles for each spec up to date, and for accuracy. It's fairly known that some specs in simcraft are not really well designed, thus producing bogus results.
- this is under perfect conditions, stand still and with all raid buffs/debuffs active

This is a list were all uploaded combat logs for heroic raids are taken into account, for all bosses.
- many bosses have a gimmic, such as often a phase where they take x% more damage
- some bosses like garajal cause skewed logs, since only the guy who actually logs and uploads his numbers are correct, the fight has 2 realms and if you are in the normal realm you cant log whats going on in the parallel realm, etc ...

Either way you can browse that site on a fight per fight basis to get a rough idea yourself. So far there is not really an agreemennt on what exactly is the best way to use this data to compare specs, since each person comes up with his/her own method.

Yet alone that this data is for heroic raid geared players. When you run heroic dungeons and do dailies you'll have 30-40 ilvls less, not to mention that the fights are completely different. Elemental shamans are at the low end of the raiding spectrum atm for example, but in heroic dungeons they are insane. Reason is that their major CD is up for every boss and that pretty much every dungeon has trash where chain lightning shines.