I remember soloing Tharsis as a Watchman Sentinel a few lvls above him, using Doc of course. I had to blow everything I had, interrupting like a madman. It is entirely doable.

I would personally go with Force Leap, then hit Overload Saber while in the air, then Zealous Strike, Cauterize and then wtv else you want. I think this is the opening sequence most people use, but I may be wrong.

As a Watchman Sentinel, this fight is a cakewalk. My T7 was geared half-assedly as well. I just completely ignored all the clones (T7 kept them busy, and actually didn't die) and stayed on the boss. With Force Kick, Force Stasis and talented Force Leap, there's absolutely no reason this fight should be hard for Watchman.