I watched Kallon later in the year when he was playing more and I thought he did ok. He wasn't Bubba Smith or anything, but he was a serviceable reserve. Given his lack of football experience, I think it would be a bit hasty to blow him off as never fulfilling his potential. If he progresses as much during spring and fall practice as he did in the regular season this year, we'll have ourselves a pretty fair country DT to put on the field, imho.
And, btw, I always discount the "you have to be mean to play DL" meme. It helps some players, but some of the best DLs (Big Daddy Lipscomb, for instance) who ever lived were notoriously good natured.