I wonder how much finishing WoT catapulted Sanderson's career. I know i hadn't heard of his books before him being revealed as WoT's writer after Jordan passed away.
Yeah, it's hard to judge. I hadn't heard of him either but I also don't follow new authors that closely. He was announced as Jordan's chosen replacement just a few months after Well of Ascension was released. This was only two years after Elantris! That's a meteoric rise, from first novel to chosen replacement for one of the best selling fantasy authors of all time in two years.
Like many, after reading Harriet had chosen him based on the strength of Mistborn, and the detailed mechanism of its magic systems, I immediately went out and bought Final Empire. I imagine I would have gotten there eventually on his own but... who can say? I'm just glad he's here and we are with him for the ride.