Blizzard wants you to progress through instances, not skip immediately to the newest instance. They've stated/made it clear they want something in between the BC and the Cata model, and currently this is what we have. The estimated iLvl I've seen posted back is what my guild expects the difficulty to be tuned at, or to say, starting around 502 and ramping up. That means heroic MGV, elite protectors, would put you at that level, any other heroics would be bonus. As well, it's the first week of the tier and you have none (or not as much as you could) of the 522+ valor gear, but you're here complaining it's too hard. So what do you want? To faceroll through content, or to progress? You're attempting content designed around gear nearly half a tier above yours if you're in 496. If you expect for it to be easy, you're in for a surprise.
The tier seemed to be released early comparing to how far guilds were progressed in T14, but I'd still likely recommend doing more T14 heroics for gear, at least the important ones/any which you have on farm, then going to T15, esp. if you're lacking gear.