Mage vs T15 : 1/12 down !
First of all, credit to Snowball the Russian Warlock, for the enrage kiting idea
If you want to solo this boss, all you need is a Frost spec, Engineering and patience. No minimum gear required, everything happens in the first 30 seconds, the remaining is spent kiting while your pet (slowly) kills the boss.
You will also need the Rocket Boots Xtreme Lite, they are easy to farm, look it up on wowhead.
How to kill the boss :
First, position your pet near the entrance, like 20 yards away. Pet positioning is critical or he will die. Put it on passive.
Second, position yourself near the exit. Spec Presence of Mind, start the fight and oneshot the deactivated golem that's the closest to the boss. You MUST oneshot him, if your Frostbolt doesn't crit just reset.
When the boss is activated, put a Living Bomb on him and use Mirror Images. Then rocketboots to the entrace, and Blink to get out before the doors close. When the golems are about to reach you, use the "double Iceblock" macro (see below). When Alter Time is about to fade, spam your Iceblock. If you do it right, you will be immune to everything until the boss reaches 100 Anima.
When the boss begins to channel FULL POWER, make your pet attack and Darkwater Potion + Rocket belt to Primordius' room.
From then it's an easy win, just kite the bolts around the room for approx. 30 minutes.
NEVER USE BLINK !! Your pet will teleport to you if you do, and you cannot send him back.
Double Ice Block macro :
/cast Alter Time
/cast Ice Block
/cast Cold Snap
Then spam Iceblock when AT is about to fade.