I had this issue with my Sentinal. Don't remeber the boss but I was over leveled also. I don't know the inquisitor story yet but my suggestion is go ahead and go dink around on taris for a bit then try again. Maybe you'll come up with a new rotation or find a better peiece of gear. Also use the stims, they help. Just take a break and come back later. You can get frustrated and hard headed after so many defeats.

Good Luck.