Palmer was the #1 fantasy QB in 2005 when he scored 318 fantasy points with a 3836-32-12 season. However, given the stat creep at the QB position, that same production last year would have ranked 12th. Palmer would effectively need to have a career best season to become a fantasy QB1 this year in ARI. He's probably a middle of the road QB2 in a 12 team league, but I really would feel uncomfortable having to start him long term.
Um, stat creep is a bit more complex than you are letting on...
In 2005, Palmer ranked 5th in pass attempts with 509. In 2012, 509 would've ranked 18th.
So if he was scoring 318/509 attempts, that's 0.62 per attempt.
In 2012, the 5th most pass attempts was 627. At his 2005 rate, that would be 392 fantasy points which would've ranked him 4th.
Palmer would effectively need to be 80 to 90 percent of the player he was in 2005 to be a QB1 in Arizona if he gets to throw the ball enough times.
Of course he'd need to be a total bada55 to be a top 12 QB without rushing the ball and only ranking 18th in pass attempts... nothing ground breaking about that. But luckily the stat creep at QB scoring is logically explained by an increase in attempts, not some magical talent influx that relegates Palmer to the back of the line.