I see what you are saying, but last season he got 0 sacks. Yes he was injured, but the NFL is a "what have you done for me now" type of league. For example: Peyton Manning went from 55 touchdowns, to 39 touchdowns to 9 touchdowns in 3 seasons. Arguably the greatest QB of all time, and has taken limited punishment.
Langford is a defensive lineman, who literally has contact every single play he is on the field. Which makes you ask this question: Is a player of his caliber (never GREAT but solid his career) worth keeping on the roster when you could clear up some cap, and also get young guys some more playing time. I think the smart thing to do is trade him for a 6th or 7th, or just cut him.
As for veteran talent, offensively we have: Luck, TY, Costanzo, Gore, and Doyle at each position group to help be a veteran presence.
Defensively: Vonate Davis, Jabaal Sheared, and I would expect Henry Anderson to become more of a leader this season as well.