Ok so I got horribored by farmign instances after I dinged 85 for the gear to queue heroics, so I went and tried to buy gear to hit 329 itemlevel average. And I noticed that there are LOADS of items to buy from quartermasters, even with rep as low as honored - and even if they're not items you actually need they will count towards your average itemlevel. I bought leather, mail, dps gear and went from 326 to 331!
I guess this might not be an exploit, but its a neat trick and I didn't know anywhere else to post it!Enjoy