Just got through it without a single death for the first time. It took about 6 clears to get there though.

I also just realized that the random summoned by paletress keeps aggro on the tank even after the fears. It shouldn't be killing your slaves. The priest does cast on the slaves though.

The interact with unit is a keybind you can set to "use" what you have selected. If you also have the option "click to move" enabled you will automatically face and run towards the unit. There are a few different threads explaining it more in depth. You hit your assist button then the interact button then a movement button to stop moving. Now all your guys are facing the boss.