There are many ways of doing this and you need to be weary of two things :
1. Don't pull the adds in purple aoe.
2. Don't pull the adds in purple aoe
The Hardmode tactic I use with my guild requires one DPS, usually a sentinel, to nuke down the warriors. For example, you kill the droids, you get bomber, you nuke walker and at 77% the sentinel takes position where the first group spawns. Usually they have enough focus, merciless slash or masterstrike is sufficient to draw the warrior to the sentinel. All the adds will run away to the highest aggro generating player. At this point the raid stacks up in a place where there is no purple aoe at all during the warrior stage. After nuking the warrior, the sentinel goes to the door, waits for the second, nukes him while the other adds go out the shield. Then , with hots from healer, sentinel travels to the final position and nukes the warrior while adds are running to the raid.
At this point you will have quite a few adds and tanks need to call our their aoe taunts or people will get killed. Nuke the adds down while healers keep the party alive. You will probably end up with 3 packs but do not worry, as long as you are in a safe spot from purple aoe things are okay. There are multiple spots, one at the right rear leg of the walker or on the right side to the wall as you enter the room.
In nightmare mode, we do things a bit differently. In this case, we use a tank to generate threat on the warriors. What do i mean by this? He will go and taunt the first warrior that spaws to the right of the walker, then he will run to the door with the bubble, peel of the second warrior, then run to the third position and take the third warrior. You will end up with three warriors and three overlapping bubbles. While the tank with hots from healers tickles the warriors, the raid, in a safe spot from purple aoe, nukes down the adds. As a shadow tank, I can keep mobs at bay under the shield with my resilience.