Pens are not an appropriate example. Their defense was quite questionable last year. They use their offense to take pressure off the defense. Every chance they get the puck they were breaking for the other end and put the Sharks on the heals. The Kings lean on their defense and break the puck out in a slow controlled manner. This is completely different and won't work for the Kings.
Forbort has had what, 5 years? He's going to be a top 4D by March? He was unable to outplay Gravel last year. Gravel? He's in the same boat. Remember Muzzin's learning curve? Martinez getting benched constantly? Are Gravel and Forbort going to be any different?
You don't have to be a complete team at the beginning of the year. Even if the Kings picked up another top 4 defender I still wouldn't call them a "contender". They would still have massive holes in the top 6 and at center. Right now the gap between where they are and "contender" is too large to make up at the deadline.
Still they were:
Pittsburgh: Goals Against Per Game:2.48 Rank 6
L.A Kings: Goals Against Per Game:2.38 Rank 3
They had pretty good stats!