Not meaning to sound argumentative because I agree with the majority of what you're saying, but here are a couple of examples that were a bit different than the typical '03, '04, '07 that you gave:
1) In 2006, we spun straw into gold with that ridiculous WR corps. One may also look at the back to back losses in weeks 8 and 9. Not only did they lose back to back in weeks 8 and 9, they lost back to back at HOME. 2 months into the season, we really still had no idea what the team was made of.
2) In 2009, we saw more of the same. 3 losses in a 4 week span that occurred in weeks 9, 11, and 12. By week 12, that team certainly had not found itself. This was at its highest point in week 11 on the road at New Orleans, when they were smashed 17-38 on primetime TV, and Belichick was famously quoted as saying "I just can't get this team to play like we need to."
3) In 2011, we saw back to back losses in weeks 8 and 9, and that was coming off of a bye! They were sitting at 5-3 and once again, it was more than halfway through the season and we really had no idea what they were made of.
I agree that they normally get off to a fairly stable start, as there's not much arguing with that point. I think things were a bit different this year due to losing the first game and starting off 0-1. Since then, we've gone 5-1, so I see the same old, same old myself.
With the next 6 games being extremely difficult, I will not be surprised in the least if they end up 3-3, which will still put them in the mix for an 8-4 record with 4 games remaining.