Brothers in Arms

With the current patch for this achiv, you just need to nuke them down.

FYI, for spawning the boss, you have to clear the two guards outside the building and the entire room.

Disposition is the mechanic of the Twin Ogron encounter that increases the haste and damage of both bosses, including the speed of their various mechanics and how much time you have to react to them. This goes up incrementally the further away you pull them, and can be seen as stages from the color of the buff they have. Green is 0%, when they are mostly right next to each other but room for a bit of space, Yellow is when the buff begins to start increasing as they are separated some, and Red is when they have gotten quite far apart and likely over the threshold for the achievement criteria.

As a result, the best way to do this achievement is to primarily tank the bosses on top of each other which gives the benefit of plenty of time to react and move from the mechanics. The downside, of course, is that some abilities will be centered right on both of the bosses which will require some additional raid movement to dodge effectively. There is some wiggle room for separating the bosses, but as a general rule of thumb, it is likely best to keep the bosses confined to the center ring in the room with the furthest distance they can be as opposite ends of that circle. Raid positioning will be key, however, as the Shield Charge mechanic can potentially ruin an attempt at this if the target is too far from the other boss. The entire raid should be mostly spread within this same ring as well to avoid that problem.

As of 7.1 this achievement is simply a dps race. Killed the boss with 3 people in total in less than a minute and was awarded with the achievement!