Use power leveling a Death Knight to Death Grip the crystals to a convenient placement, and punk drop the green puddle by destroying the crystal. Your mana-needing folks stand in the puddle until they have about 5 stacks or so about power leveling. (5 stacks are getting you 1,600 mana every two seconds, but you are taking 1600DPS.) Try and time your vapor use, however, so that you always have a crystal available for use to get power leveling.

Searing Flames must be interrupted. It is going to be bad, bad news for your tank if you let it get cast. With a leisurely 2 second cast, though, none of your usual interrupters should have any trouble with that power leveling. Surge of Darkness looks pretty scary, but you just need to have a cool down ready to handle it. It pops about once every minute, and just heals through.

Mark of the Faceless is your usual "do not stand in this" test, but slightly modified to "do not stand next to the guy with Mark of the Faceless." (Cmon, he is faceless. You would not want to cuddle up to that anyway, right?) For this reason, most raids like to spread out a bit, giving everyone room to get away from the freakish, faceless monstrosity you have become. When Shadow Crash hits someone to get power leveling, get your big spell-based DPS inside the black puddle left behind. While inside the black puddle, your raid members will get a big casting speed and damage bonus. Healers want to stay out, however, since it will also reduce the amount of healing you do.

A lot of this fight will depend on your raids ability to position intelligently and react quickly. Nothing that Vezax does individually is unique and new to you. You have stood in buff-giving circles before about power leveling, dodged void zones, and gotten away from explosive raid members. The trick here is to do it all at once.