When I first started playing, I did not really know there was a certain way you were "supposed" to level your characters' roles up. I did Noel COM 1-99 then SEN 1-99, and Serah RAV 1-something, MED 1-99, RAV something-99. I've read that i'll have little to know problem finishing the story, but would I be able to do the side stuff and DLC or would my stats be too messed up? I'm over 20 hours and would hate to have to start over, but it would be better than having to start over after 60 hours. Thank you for your time.
You will still be able to do everything in post-game including DLC. You'll definitely have more trouble with certain enemies but good monsters and good strategy will more than make up for your poor stats.