Bring stims, make sure you have enough to heal yourself. In beta there was a medical droid not too far from where the Emperor was. You should buy the stim that increases your endurance as well. Make sure T7's gear is up to date. Lastly during the fight, make sure you los (line of sight) the emperor and his images. The images can be killed with a few normal slashes. Save your stuns for the emperor himself. T7 may have to die but it's for the greater good
*If you still can't do it, don't be afraid to ask for a friend to help*