I noticed he is playing in the 2nd tier Swedish league. Is he a legit prospect, or a guy just having a good year against inferior competition?
I say he's a legit prospect. That he's playing in the 2nd tier shouldn't reflect too much on him. In his post draft-year, he the plan was for him to be one of two regular goalies in Brynäs (SHL), but his preseason and the beginning of the regular season was spoiled by some illness (not sure what it was) and injury that kept him out of play. With Johansson out, Brynäs brought up another goalie from juniors, Felix Sandström (Brynäs have been spitting out goalie prospects like crazy for a while), and Sandström seized the opportunity.
After battling illness, Johansson got back on the ice, and because Sandström was doing well in SHL and Johansson needed ice-time, he played with Brynäs junior team. And then it was decided that the best move for his development was to lend him to Almtuna in the second league (Allsvenskan).
In the following season they kept him in Almtuna and played Sandström and veteran goalie Bernhard Starkbaum. And this year they brought in another vet in David Rautio to share the load with Sandström. So Johansson has gotten kind of stuck because Sandström is playing so well and Brynäs don't want to put the load on two young goalies. It all dates back to that illness and injury prone post draft-season.
I guess the Sabres are OK with his development. If they weren't, they could have stepped in and signed him so that they had a say in where he'd play. I wouldn't worry too much about him playing in the 2nd tier either - it's still a league that holds a pretty good standard and I'm sure Brynäs goalie coach is monitoring him.
The situation is actually familiar to when Jakob Markström and Anders Lindbäck both were young goalie prospects in Brynäs. Lindbäck was "first in line" to get to play for Brynäs but was sidelined with illness too. Markström seized the opportunity and Lindbäck was put on loan to... Almtuna. And while Lindbäck never established himself as an NHL goalie, he still developed into a good goalie. Let's just hope Johansson turns out a little bit better.