Just did Foundry SM, on my Jugg/dps, we had a tank that ran ahead of us passing mobs, whether he/she realized that the healer(sorc) and I could not stealth through the mobs was very amusing. The other dps was a stealther which made it easy with organic npc's but when we got to the parts with all droid mobs he still ran off way ahead of us. The healer reminded the tank that we were not able to stealth through certain areas but tank still ran off would come back and attack, since we were not following him/her. The healer/sorc decided to quit group after the tank would not listen. Tank finally dropped off because I guess he/she was tired of us not being stealth. Tank did not give a reason for leaving group. We got another tank and got through the instance just fine.
Also, why do Sin tanks/dps feel the need to do Overload to start a fight? All it does is kick all enemy NPC out of any AOE that is being used.