Dunn had 9 total TDs in 2002. Vick rushed for 8, Duckett rushed for 4.
Dunn had 5 total TDs in 2003. Vick rushed for 1, Duckett rushed for 11.
Dunn had 9 total TDs in 2004 (all rushing). An injury plagued Vick rushed for 3, Duckett rushed for 8.
Dunn had 4 total TDs in 2005. Vick rushed for 6, Duckett rushed for 8.
Dunn had 5 total TDs in 2006. Vick rushed for 2, Norwood rushed for 2, and Griffith rushed for 1. Vick also passed for a career high 20 TDs, compared with 14-16 in his previous full years.
So bottom line, Dunn has had his TD opportunities limited by a couple guys who averaged over 12 TDs a season combined from 2002-2005. The Atlanta running back can still score TDs, it's just that Dunn hasn't been the guy to do it. And in 2006, the whole offense was down.
I don't think Dunn is anything more than the sentimental favorite to win the starting job. He had his worst YPC as a Falcon in 2006 while receiving the most carries of his career. He is now 32. He's got a new head coach, and there's a running back who's been getting all the first string reps for the last month. Vick and Duckett are gone.
The real questions are, first, do you want the Atlanta running back this year? The offense will be completely different. There's just not enough information right now on how well Atlanta will do with their crappy passing game and whether Norwood or Dunn is good enough to open lanes. I don't know if Atlanta can even put together a mediocre offense, with wide receivers who have never had a real quarterback before, and a quarterback who has never lived up to expectations. But if they can, Norwood becomes more desirable.
And second, is Norwood good enough to be the reason that Atlanta has a good offense. In my opinion, Norwood has an opportunity. If he's good enough - and he was considered one of the top running back prospects in his draft class - then he may have a chance to take the job and run with it. That's the bigger question, not whether Dunn will get the carries of whether there will be a goal line back. If Norwood's any good, and/or the rest of the offense performs better sans Vick, Norwood will be a good value. All the rest of this conversation is window dressing.
Right now, I would put Norwood in the upper middle of the lead-runner-in-their-RBBC category, ahead of guys like Deshaun Foster who have had a chance to produce but failed, and ahead of guys who would need an injury to take the starting job outright, like Tatum Bell (if Jones returns). He's a little more valuable than DeAngelo, because he should be the starter, he's just as young, and similarly talented. But he's not as valuable as a guy who straight up holds his job.