It really feels like the luck of the draw sometimes as to if that add phase will be easy or chaos. Normally what happens straight away when they spawn is they aggro on the healers since regens and MT heals will happen. I usually try to pop shroud as they spawn if possible to lower my threat but normally it won't take them off me. Hopefully the red one will be close enough for the OT to grab the thing and move it because once the green one gets to the DPS all hell breaks loose and group healing begins drawing loads of aggro.

Sometimes what i see happen is the OT can't get aggro fast enough and both adds massacre the DPS and healers. Personally only know of the strat involving ganking the healing add as fast as possible while the OT tanks the red one and the MT tanks garuda in a sort of triangle formation though i have done a PuG where the MT took both Garuda and the red add while the OT took the green allowing for a faster kill and then took red off the MT.