I think that's just the nature of the beast. East coast storms are usually terribly complex scenarios, often with lows transferring from one to the next, where the coastal low actually forms, how quickly it can deepen and form the CCB that usually provides the meat of the storms has great impact on the ground. That usually means a pretty narrow stretch of the heaviest snows, so slight storm track differences have a huge net effect on snowfall totals and intensities.... not to even mention precip type. It's amazing the forecasts are even as good as they are.
I'm not sure the busts are that much more horrible in the south. The last couple years alone have featured some big busts for NYC. The southern areas due to their climo are always more at risk. They have more temp issues and they are closer to the coastal low initialization, so the storm usually doesn't have as much time to mature for them. If the low location is not south enough, or if it doesn't deepen in time, they are screwed.
Just give me CAD and a nice juicy low pressing into the OH valley.