You may have a point about PP time (I don't have the numbers in front of me), but his ice time did increase from last season to this one. So basically what you're unintentionally saying is that he's ineffective at even strength, since an increase in his overall ice time and a decrease in his PP ice time leads to a ~30% reduction in his point production (and yes, I factored for games played).
Rundblad was definitely lights out, but Larsson's poor defensive positioning, his problems with gap control and angles, his turnovers and his poor footspeed no doubt had a strong influence on any decrease in Larsson's ice time in key situations. If what you're saying about Larsson's PP time is true, then it's even more damning evidence against him, as Larsson's offense is obviously more of a selling point than anything else.
I think the fault you're making is looking at statistics without knowing the little facts of how Skellefteå worked. During the regular season, the first line of Skellefteå was hands down the best line in SEL:
but they were also the only line on the team really producing offensivly during major parts of the season. The second line, on which Larsson played, didn't get its production going for quite some time and was used as the shutdown line, usually matched against the opponents best players. So basically what I'm saying is yes, he was ineffective at even strength, but that wasn't their main job for the greater part of the regular season. I think anyone who has followed the SEL could tell you this.
What games are you basing this on? He was awful in the SEL-finals, if you're basing it off that, but so was the whole team.
His decrease in PP-time came mostly from Rundblad becoming the best offensive defenceman in SEL and Erixon having developed if not the, then at least one of the best slapshots in the league.
Then ofc we have the whole matter of him being troubled with injuries and playing less games than last season.
I'm not projecting him to be a new Lidström or anything; just saying what I know.
Just like Pierre Dorion says here:
http://www.youtube.com/watch?v=f5SS1EDRJUU&feature=youtu.be&t=2m20s I think the main thing Larsson has to do is mature off-ice, learn english and all of that, before he goes to the NHL. If he stays in Sweden he'll probably get to play in all situations as well with Rundblad and Erixon gone, so it would probably be for the best if he's drafted by a team who can let him stay for another year.