I think the bigger note is how Armstrong really wasn't able to keep above the water in mixing up his talent and making his additions, that was the whole point. Little by little they lost a lot of their identity, lost a lot of talent overall (especially on defense) and it's hard to recover from that. A coach does need to adjust and get the most of players though so I think he does deserve some criticism.
It will likely be a priority for the Leafs to not screw up with their defense again. There are plenty of good names potentially heading to free agency. They need to get it right. I think Woll will be more than fine, but maybe I'm just optimistic.