I've done the mini boss and the droid boss with just two people (droid video: http://www.youtube.com/watch?v=dZfArbwsMzY&feature=plcp
). We gave Sav-rak several attempts, but we couldn't reliably get him off the pillars. Campaign geared companions, campaign/dread guard geared players, shadow tank and commando dps.
Congratulations on your achievement! How many attempts on Sav-rak did it take before you got lucky on the pillars?