I came in second behind a very well geared and very talented hunter on Naxx 10 trash last night, clearing the Plague and Military wings. However, we had the tendency to aoe-mosh-pit everything, and consecrate and holy wrath certainly help pad the damage meters there.
On bosses, I was at the bottom, but still pulling respectable dps.
The only dps ever to be below me on a boss was an elemental shaman on Loatheb.
I'd roll my eyes and say "what's wrong with that guy" if I didn't use to be an ele shaman myself and understand exactly what they're talking about with their damage and scaling woes.
Additional thought:
Your dps on heroics should be a direct function of the size of your pulls and whether or not you use cc, as well as the abilities you use.
There's not much sense in bragging about top damage when it's hard NOT to be hitting 4-5 mobs at once.
You really ought to be thanking your healer who's probably sweating it out every time you Captain America Shield half the dungeon for your gross damage output.
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Fionneous, 80 Blood Elf Prot Paladin, Draka
http://www.wowarmory.com/character-sheet.xml?r=Draka&n=Fionneous