It's always Tam Tara or Totorak for me. Or at least most of the time. Once in a blue moon its Hakkue Manor and Stone Vigil has only showed up once for me in the Roluette. And when it chooses bosses its Titan most of the time, Rarely Ifrit. NEVER Garuda. I haven't seen normal Garuda in ages. I even forgot how she fights. xD