During the fight as explained below Thaddius will cast Polarity Shift, avoid going into the opposite charged area and you will get the achievement. It is more of a disciplined raid group strategy, if everyone is on the same page then you should be ok. A good strategy is to split the raid up in groups, one charged group moves clockwise and the other moves counter clock-wise.

Thaddius Abilities

1. Ball of Lightning will occur is no one is in melee range, hitting the tank for 17,500 - 22,500.
2. Berserker Enrage happens after six minutes, this will increase damage by 1,000%.
3. Chain Lightning is cast every 15 seconds and hits 5 random raid members for 6,900 - 8,000 nature damage.
4. Polarity Shift is cast every 30 seconds and will charge the raid positively and negatively. People on the positive side will gain a 10% damage buff, the negative side will deal 3,500 damage a second for two seconds to members negatively charged.

Thaddius Strategy

1. At the start of the fight you will be facing Feugen and Stalagg. These two mini bosses need to be killed with in 5 seconds of each other or the one alive will resurrect the dead one. The tanks need to keep them in the center of the platform, if they leave their platform the raid will wipe. Every 20 seconds the tanks will be thrown to the opposite platform, the tanks need to position and gain threat immediately. Healers will now be healing the opposite tank. Split your raid in half, time it right and you will do fine.
2. Once Feugen and Stalagg are dead the raid needs to jump onto Thaddius's platform. The tank needs to initiate him and place him in the center of the room.
3. The raid should determine which side the raid member with negative and positive charges should go to. When Polarity Shift is cast everyone needs to go to their respective side, determined by their charge. Stacking the positive charge is vital so that the raids damage is high enough to kill Thaddius.
4. A positive charged member going into the negative charged area will shock raid members that you pass, be careful to avoid this. Moving in a clock-wise or counter clock-wise fashion works best.
5. This is a very healer friendly fight and will not require as many healers as usual. This means healers can DPS during the fight.