Yeah, the D is a mess. It's Doughty, a honest 4/5 in Martinez, and then a lot of not a whole lot. Anyone not named Forbort or Phaneuf are total wild cards. If just 1 of them becomes an every day top 6 on a competitive NHL team, at this point, it'll be a win. Then there are still 3 more spots to fill, assuming Martinez doesn't go anywhere, and that Forbort and Phaneuf simply aren't good enough.
Add all the talent you want up front, nothing is getting better until they fix the defense, and if Doughty plays the way he did this year again, they're 100x further away than if he plays great. Of course good defenseman are the rarest of commodities, so nobody is going to hand you one. Have to find one in the haystack like Muzzin, or have a risk like Mitchell work out great. Regehr wasn't necessarily cheap, and he was already 33 when he got here.