Tbf, Allvin was an AGM with Rutherford for a grand total of 12 weeks, so can't really say much about him and Rutherford as a team.
And I feel like his scouting record holds up. Becomes a European scout here in 2006, only European taken in the first three rounds we've busted on since then is Samuelsson - even the incredibly silly Bjorkqvist pick that Rutherford took in his muscle mary days looks like it's paying off as well as it could for an uber-reach with injury problems (although if he recced picking him in the 2nd, boo that man). Hard to know how much input he had in guys who'd already moved to North America but Kuhnhackl, Sundqvist, Kapanen, Simon is a solid body of work for the rounds they were taken in. Gustavsson seems to be on his way to joining that list. If he does, that's 4-2 on wins for Euros in the first four rounds. And I'm too lazy to check whether they were drafted from Europe or not, or whether Montreal had another European scout then, but Allvin was a Montreal Euro scout when they took Halak, Grabovski, Streit, Emelin, and both Kostitsyns (they only made 4 other Euro picks in that time).
Allvin takes over as Director of Amateur Scouting and we immediately start taking skill players, although can't be sure how much that's him and how much is Gentleman Jim changing course. Obviously we don't know how he really did with those drafts yet, but if one of Addison and Hallander hits I think 2018 hits expectations and Addison seems to be close; 2019,the Quebec two finally seem to be working out the AHL and Puustinen already represents a hit for a 7th rounder; so far the first 4 picks in 2020 are tracking well; and I think it's Pryor's baby for 2021.
Also I don't think Allvin ever ran WBS. The initial press release for his promotion to AGM mentioned nothing about it, just that Erik "Who" Heasley would continue as AGM of the WBS Penguins. And even if he did... he was interim GM in Pittsburgh 12 weeks later, and I doubt he did both. And google's not saying anything about him getting the role when Hextall got here, and neither the Pens or Baby Pens Front Office pages mention it.
Him as a GM would be an eyebrow raiser if it was anywhere other than somewhere with Rutherford as his boss because he's not got that experience and it seems pretty likely Rutherford's going to be a hands on boss. But I feel like everything that we know he probably did went well, and that he was able to climb the ladder as someone with zero profile or connections is hugely to his credit.