He's 21 damn years old. To even insinuate he's "done" is beyond premature. On that same note, he may be done here. For whatever reason he has not grasped whats required of him when he plays and sometimes doesn't seem to be using his head. It may be a case of him needing new voices and instruction.
I think a better comparison than Hedman may be Alex Edler. Also Swedish, drafted in the 3rd in 2004 (age 18) and took 3 years of NHL duty before it really clicked for him Jack Johnson is another one and much more comparable to Larsson in terms of draft position, who started very slowly and also took to age 22 before it "clicked". He played on a few really bad teams in LA as well. Kris Letang is another one who was thrown in young and took a few years to "get it" but he also had the luxury of playing with guys like Malkin and Crosby too. The one difference between all of these guys is that by the 2nd or 3rd year they were playing regularly (60+ minimum).
There are plenty of guys that have similar trajectories. 2-3 years of regular NHL game time for a young defenseman is not uncommon, which is something Larsson has not had here obviously.
I personally think he needs to go to a team that needs him more than we do especially now that we have Severson and Merrill really starting to grow, a team that will play him every night and let him work out his growing pains, a team that is basically bad right now. He's far too young and obviously has a skill set that if he utilizes correctly could be very good, he just may be in the wrong place for that to happen.
Its very possible he is a total bust and done, but its just way too early to say that definitively.
anyway, time to go catch the PATH