The biggest problem with this argument is there is no real advanced statistical info I can find that says he actually was good on the Islanders.
There isn't much evidence Leddy's play really dipped in Detroit, so much as he just happened to move away from a Barry Trotz coached team which always managed to outprodue there advanced statistics. It is true he is good in transition, but that's basically his one real defining skill at this point. The rest of his game isn't good enough, and he's past 30 and multiple years off from his peak already.
We are also in a pickle here. Because let's say he does show up and play well for a stretch. We saw what happened the last time we made a trade to fill a gapping void on D and the player came in and played well for a short amount of time: Army over reacted to a short sample size and committed too much money. So even if he plays well, it miht not end up being good for us past this season, and I don't think this really does anything to get us over the hump into being a true contender.
Hmm... This reads real doom and gloomy, but that wasn't my intention. Basically, I don't despise this trade overall, but I just wish we picked a lane. This is a hedge trade, to me. It feels like Army knew he had to do something to get a LHD brought in no matter what, but the market was very seller heavy, and he decided to not touch the Gio prices, which I can understand. But I also don't see a good road forward either. The value is clearly not very good imo, but we've been surprised before. If the idea is to give us more cap room to get the LHD fix this off-season, then I also don't really buy it. If we get an upgrade there in the off-season it would have been through trade anyway, unless we are all confident going into next season with 37 year old Alex Gologoski as our partner with Colt. So giving up Sunny and a 2nd for Leddy just feels off to me, like Army felt like he had to make a move but ran out of names and this was what he was left with.
I don't think it's fair to compare what happened with Scandella to Leddy. The entire team was in a panic after what happened to Jbo, not just Armstrong.