This sentence makes my head hurt. The defense stinks because it's average to good at best? That doesn't sound stinky.
For me, the three biggest keys are 1) Jones, can he be an average starting goaltender; 2) Coaching, will they be aggressive enough offensively, will they fix up the PK, will they utilize the roster correctly; and 3) Logan, can he get back to being the defensive stud he was in '13-'14.
If Raffi can come back, that would be a huge bonus. Obviously Hertl, Nieto, and Tierney need to step up and Marleau needs to rebound. But those things seem reasonably certain to me.