This post helped me a ton. To anyone who reads this, this advice helped me a ton. So much in fact that I was able to continue refusing Valkorian's power. What I did is I hid behind the pillars in the main room, you have to peak out to bait him to use his Turbulence. If you just hide behind the pillar his AI will seek you out and then you're screwed. You want to poke out, send out any and all dots you have during the 2 second cast time, then hide behind the pillar before he casts it. This strat worked perfectly on my Commando. I believe this strat can work well on any ranged class. Melee classes, sorry but I do not believe this would be an effective way of taking him down.