No, he was just following Machiavelli's advice for how a prince (ie dictator) should enforce law and order when extreme measures are called for. Namely assign the job to a henchman, and then when the deed is done, convince the people that the henchman was acting on his own, and execute the henchman:

http://faculty.cua.edu/pennington/churchhistory220/Lecture13...

One would surmise that if Stalin's goal was to avoid building a reputation as a brutal mass murderer, he certainly failed.

No, Stalin's goal was to maintain control without open rebellion.

He succeeded in that.

There's good evidence he was poisoned, and after his death he was pretty quickly denounced, but he ruled for long enough that we can still count it as a win I suppose.