Little more detail on Boss 2:
Yash spawns adds that are on the beds at certain points in the fight; the lower her hp, the more adds spawn. Minimum of 1, maximum of 4. Now you don't have to actually fight these adds. What we do is put the ranged dps and/or priests at the 4 beds in the room. One at each bed. When you see the little cone descend upon an add, you know that will be the add that will be summoned. The dagger in the bed has to be clicked 4 times; after each click it becomes unclickable for a few seconds I believe, so you have to wait; this is why you have to start clicking early, when the cone shows up. If you successfully click the dagger 4 times the add will turn green when it spawns, and help you during the fight. Some use skills (if you press k you'll have a pet skills window for the add), and some just help by themselves. I've never actually been able to use the pet skills, possibly because I'm usually tanking and am not the one clicking the daggers. To note: EACH TIME YOU CLICK THE DAGGER YOU TAKE DAMAGE. This is normal, you have to heal or pot through it. This is why we generally either put priests on the daggers, or I'll call out priests during the fights to heal up the dagger people if they aren't already.
As for tanking the boss, I've tanked her pretty much... everywhere. For us though, we tank the boss near the middle of the room, so that when the priests are at the beds I'm still in range of everyone.
Boss 3, agreed with Gamegenius. Stay balled up tight, have the tank wws/tab holy strike or whatever he does to grab aggro on the add(s) that spawn. It seems the slower you kill him the more adds he spawns; i.e. the longer you take the harder the boss fight becomes.