Spent my afternoon trying to do the only achivement I was missing from both Ulduar formats: Shadowdodger 25.
EDIT: All of it was done as Enhancement;
I cleared every required boss in 10m solo to do it (Thorim was annoying to figure out at first) and then switched to 25 Mode for Vezax. Spent around 10 wipes trying to figure out a strategy and managed to pull it off:
You pull the boss, stand in melee range and let him cast EVERY SINGLE SEARING FLAME.
He will continuously chain cast them over and over untill either hes dead or casts Surge of Darkness;
You will want to kill the clouds however or you will start the hardmore and you will wipe.
To heal through the damage you will need - I kid you not - Conductivity.
Yeap... Conductivity. It turns out both Healing Rain, Healing Stream Totem and Conductivity escape his Aura of Despair rule.
In short you stand near him 70% of the fight MSW5 Healing Rain on both of you doing your normal rotation and killing every single cloud you see.