I think a lot of the goal disparity is due to:
1. Penalties (for and against
2. Injury
ppo - power play opportunities, ppoa - ppo allowed
Team
PPO
PPOA
Man Games Lost
St. Louis Blues
206
250
249
Dallas Stars
226
214
131
Chicago Blackhawks
221
202
94
Its hard to score a lot of goals when your constantly killing penalties and filling in with whoever is healthy. (Paajarvi on the top line? Remember that?) Blues have yet to really have their full team on the ice this year, and have played more time on the pk than the other two contenders in the division and they're still right there with them . Since Jan 1 they have been the better team.
Dallas has a terrible D that has been bailed out by their offense, and I think that will show in the playoffs.
Chicago is disciplined, healthy, and can score. I think they are the more dangerous team.