Well, the idea is you are supposed to go from 500 int at level 70 to 1500 int at level 80, thereby providing the same "boost". Some classes, well, most, are insanely gear dependent. Mages, boomkins, warriors, etc. If you don't have really good gear, your DPS is going to be bad and you won't be able to kill players with good gear.

In our 10/25 man raids usually the #1 spot alternates between a hunter, a boomkin, a mage (me), and a 2h arms warrior. A boomkin can put out CRAZY damage, but you do need the gear to back it up. With the huge HP most people are running around with, even teams of 2-3 can't really kill a single geared person unless they can approach similar gear levels.

The good thing is that its not super hard to gear up, it just takes time and patience. Heroic end-boss drops and badge gear is on the same level as Naxx10 level gear. There abounds tons and tons and tons of great crafted epic gear. There are BoE epic drops from 25 man instances that can be bought. You just need a ton of time to farm the gold/mats/etc to buy the "best" things you can. And in that sense, WoW definitely rewards those who put in the most time, but not sure how else it would be done in a item-centric game like that.

That said the arena games are completely different from other things right now, and revolve around massive burst damage and survivability talents (iceblock, bubble, anti-magic, etc). Boomkins don't really have massive burst damage (DoTs) nor really high survivability so they will be near the bottom of the current arena totem pole. Ele shamans and warlocks suffer pretty much the same issues. We'll see what happens when things slowly get rebalanced with patch 3.08 and on, but its going to take a lot of time.