Are you watching over-the-air, via Cable (Comcast?), or via Satellite?
After reading this, I noticed that (at least this morning), the separate feed going to Comcast was not taking the NBC audio direct (no processing) but was getting re-processed and re-balanced a bit. (Operator error in programming the automation events).
When we take a DD5.1 source, like HD NBC, or the Conference Center ("Music and the Spoken Word"), the audio is sent to the processors with a command to pass the audio "as-is", with only an overall level-reduction if needed to prevent over-modulation. The dialNorm is fixed at -24 dBFS on everything.
The local Promo spots are a totally different issue. The promotions people seem to think the audio should be "set to 10" when they record them. Master Control has complained about it quite a bit, so now we have one of the engineers looking in to it. The local promos should be running somewhere around -20 dBFS, and the processor should try to normalize it to the proper Dialogue level. If the spot is coming in WAAAY hot, it's probably out of range of the processor for the first moment or two. Of course, then, the processor has to "recover" as the next spot (with the correct level) comes in, so it becomes very noticeable.