As a rogue with ilvl 520 as well, it took a few attempts (about 10, I think). But I was done in less than an hour.
With all the weeks grinding valor, sigils, secrets, and runestones, I liked the actual fighting. Even the celestial blacksmith fight took a few attempts. Makes me feel a little more like I've earned the rewards.
Getting used to kiting the adds and using Shuriken Toss (the first time I've ever used that talent) took some time, but I was able to avoid the ground AoE (most of the time) and the adds and Wrathion's frontal attack.
Between waves of adds, I nuked Wrathion, then went back to running away. Fan of Knives on the images. Switching targets on the adds to apply Deadly Poison on as many as possible. Using combo points for Recuperate. Kidney Shot on Wrathion when I could, for the extra damage from Prey on the Weak.
I also had leeching poison, sea mist rice noodles, spring blossom flask, and drums of forgotten kings. Save defensive cooldowns for adds (they will catch up to you eventually). And just nuke Wrathion when you have a clearing.
All in all, I think my DPS was about 80k total. As mentioned, I think, there's no enrage, so focus more on surviving. You can also vanish without resetting the fight, so if you have Cloak and Dagger, you can use it to close the gap between you and Wrathion if you need to interrupt something. But he tends to jump to you anyway. Also, I did notice that he kept facing me, so I couldn't get behind him to attack, except when he was casting his frontal attack.
Or you can wait until you have ilvl 530+ and nuke him while completely ignoring the mechanics.