I'm not either, but I'll give it a go. Its hard to say what Gunnarsson's advanced stats should look like because he has been used very heavily in the defensive zone. He has 17% O-zone face-offs. I don't have a good stat sites for QoC yet, but I'd say he also has been out there against better comp. Based on the eye-test and starting line-ups (lacking a good most common linemate site), he has been paired mostly with out two big defensive guys in Parayko and Pie. They have been easing' Pie's workload by shifting the defensive responsibility more and more toward Parayko (again, eye-test), so Gunnar is along for the ride. Those two factors are going to heavily skew advanced stats like Corsi. Comparisons to Dunn, who has been sheltered and getting 40.5% Ozone starts, are going to be naturally skewed.
That said, Gunnar is actually pretty good. He is last on the team in CA/60 with 71.47. Dunn is 2nd with 58.68. Gunnar is also last in CF%, Dunn is 3rd. That's to be expected given all the D-zone starts. However, given such high Corsi (attempted shots against) he is actually very low on Scoring chances against. He is 2nd to Parayko in SCA/60 and SCF%. So lots of shots, not a lot of scoring chances. This is probably due in part to his high # of blocked shots which count as a Corsi event, but not a scoring chance (1st on team in blocked shots). There is also not a lot of high danger chances against as he leads the team in HDCA. He is also getting a good goalie save percentage as well, through luck or funneling chances to the right areas. Consequently, bottom line, his GA/60 and GF% are very good. Both 2nd on team to Dunn (who is heavily sheltered).
My interpretation based on eye-test and these stats, Gunnarsson is being asked to do JBOs job, or at least pick up a lot of the slack taking the heavy defensive LHD role. Most of this is a consequence of being partnered with Parayko who is getting more defensive responsibility. They are understandably giving up a lot of shot attempts given heavy defensive play, but they are limiting scoring chances due to steady defense. Even the chances are being funneled to places the goalies can make saves. Given the defensive work-load, it is very admirable that he has only been on ice for 2 GA 5v5. He's made some PK miscues, but his 5v5 has been remarkably steady given his role. And this is coming from someone who was hoping the stats would tell me Dunn was better, and Gunnarsson was over-rated. That's not the case, Gunanr has done remarkably well from a stats point of view in his role so far this year.