To answer this question take a look at 80lvl twinks. They get super high ratings on secondary stats, this way being super-overgeared. And you'll see that fire mages get the most epic overdrive. Like soloing Algalon.
You are confusing bad with mediocre...just because you don't get a 20k dps increase from a new weapon doesn't mean you scale bad.
You are confusing mediocre with bad. Relive is 100% correct in his statement.
An example would be Cataclysm.
First tier: Survival way over every specc cause of great talents/passives providing us with 15% more agility and our lovely AotH that gave us around 2k attackpower. That's a headstart no other class got and we reigned supreme.
Next tier: Survival did not scale for shits, static Attackpower being one reason, but having our shots scale with attackpower aswell. Marksman took over as the best specc due to more gear = abit better scaling, but still not terribly good. middle of the pack as it's known.
Last tier. Marksman supreme in the first months untill survival got a well deserved buff. Still we were sat out on the attackpowerbuff in Dragon soul that made us fall behind by ALOT. What was their reasoning? Yeah, gear will fix it. and they admitted in the very last months of DS that Hunters were behind so they buffed up by around 10% (Which we would've had if we were to recieve the AP buff in Ds aswell)
Surprise surprise we scale bad with gear, and you can kiss my posterior good sire.
On Topic: Fury warriors depends on weapons alot and other parts of gear aswell.
Boomkins.. they havent even started to scale yet =). from what i read pre launch it was predicted that boomkins would not start reaching proper haste/crit before tier15 normal bis.
Though i havent read up on boomkin theory craft after launch as a last minute change was made and i went mage. Witch brings me to another strong contender, Fire mage. I dont know if they classify as gear dependant in the same sense as boomkins. Boomkins needs gear, even more than available atm, while fire mages just scales so insane.