They don't suck. Sucking doesn't equate to being average or slightly below average. Schenn doesn't suck, Bear doesn't suck, Dermott doesn't suck, and Burroughs doesn't suck
Well considering their offense isnt bad, yet their still the 6th worst team in the league, I'd consider their D- Core pretty bad, Hughes is the only one I'd consider good and even he is a 1-way player.
Bear has been their 2nd best Dman and He is probably a #4.
The rest have been 3rd pair caliber or worse.