Hi guys,
idd dont worry about losing aggro on the droid, he taunts a lot as well. Thats his purpose. You could try a normaL group and see if you can hold aggro there. And a small tip, put your shield on a high dps melee, like a sentinel. They stay close and get the benefit from your shield and moreover you lower their threat.
Its a shame there are no good guides out atm, but statswise most important is mastery and defense.
Make sure you got your accuracy at 110% and that your gear is augmented.
For rotation your can use this:
http://dulfy.net/2015/10/29/swtor-4-0-immortal-juggernaut-pve-guide-by-artorias/#Rotations
Good luck and keep tanking. we need more of em!!