I don't think that Sweeney should get a pass for not seeing that all his young guys would regress. The term 'sophomore slump' was coined because it's so common.
If I'm going to give him a pass for anything it's having so many injuries early on.
I think the things that have gone wrong with this team should have been (and probably were) expected to a degree. I also think Sweeney got a lot of things right this year. Moore, Halak, Wagner, even Nordstrom have all been really good additions (even though Cassidy leans on Nordstrom WAY too much).
I think Sweeney is trying to balance patience with the the standings and how they're trending. If he could, he'd wait until the deadline when he has the most cap space and the sellers are up against a wall. I think being 3rd in the division allows him to be patient, but he's also probably feeling that luxury slipping away with each point left on the board.
I also think the veteran players are getting frustrated, for good reason. They play their bags off most nights and have to wait and wait and wait for help to arrive.