You Runed Everything!

I cannot emphasize this enough. Instead of watching the colors on the runes change, look at the boss. The REVERSE ORDER of the colored buffs is the order in which you should kill them.

So purple, red, green, blue, yellow should be killed yellow, blue, green, red, purple.

Update: Based on the below comment, this technique works great when you're alone, but may not work in groups. If you are in a group, I suggest having your group leader pull and following the colors they see (although I can't promise it'll work).

We did this Achievement today and we figuered out how it works.

1) Get into phase two where you fight Odyn.
2) Wait for "Draw Power".
3) The runes on the floor will shine up one after another.
4) Kill the adds in the order of the runes (Example: Yellow shined up first. Red second, etc. So you have to kill the yellow add first, the red add second, etc.)
Now you have a Debuff called "Runic Mastery" which guarantees you get the Achievement after killing Odyn.
5) Pop Bloodlust and get Odyn into the next phase without getting a second "Draw Power".
6) Kill Odyn. Don't die.

Achievement earned. :-)

We had a bit of trouble with this at first in our group, so hopefully this helps:
1. Get Odyn to phase 2 (where he comes down)
2. DPS him some but don't push below 60%
3. Before Draw Power, the runes that the adds go to light up briefly in a certain order, memorize this order
4. When the Runebearers come out, drag them onto the runes IN THAT ORDER, then ALSO kill the adds in that order.
<<If Done successfully,You will get a debuffed called Runic Mastery, IF YOU DIE OR USE AN IMMUNITY YOU WILL LOSE IT AND NOT GET THE ACHIEVEMENT (personally, everyone else will)>>
5. Get Odyn to phase 3 BEFORE the next Draw Power
6. Kill Odyn
7. (optional) laugh at the shadow priest that used STM and didn't get the achievement because of it (<3)

You can have all the adds on the runes at once, so long as they are dragged onto and killed in the correct order. e.g. you don't need to kill add 1 before dragging add 2 onto the rune.