Looking at the goals per position:
It's going to be slow going progressing some types of defenders, since so goals are based on tackling numbers.
For example, Pat Angerer:
85 tackles | 500 xp
110 tackles | 5000 xp
125 tackles | 10000 xp
For reference: 85 tackles in a single season would have led the league in any of our Madden league histories.
Sacks however, are less suspect:
Robert Mathis:
3 sacks | 500 xp
6 sacks | 5000 xp
12 sacks | 10000 xp
Additionally, it seems like based on what kind of XP earn rate your player has - which you can check by scanning through his packages list, you'll notice that if you "earn more XP" what it really does, is increase the rewards you get for reaching these milestones.
So maybe a "Superstar" sacker would get 20k xp for 12 sacks (it also might be prorated somewhat to allow for younger players to progress faster).
For instance, Jerry Hughes (a bum), would get 20k xp for 10 sacks.
Offensive Lineman progression is interesting.
A lot of their goals are based on things like: Rushing TDs scored, Passing Yards generated, game-to-game it's things like first downs, yardage (rush or pass)