Why does this just scream "Monty Python"? Since our 6-int wizard, we'll call him Thag, will need to be very selective in applying his 1 skill rank per level, and Concentration is one of the most useful non-Int-based skills, it would make sense for him to max it out. I can picture it now ...
...
(camera fades in to a sunny field surrounded by trees. Three dirty and bloody warriors [Bob, Dave, and Chuck] battle against half a dozen fearsome orcs. The sound of swords clanging fills the air, and the sun glints off their weapons. Off to the side, seemingly ignored, is a tall, dim-looking man holding his temples and staring intently at the battle.)
Bob the Fighter: Thag, get in here. We're outnumbered and need you.
(The battle continues for several moments. One of the orcs is slain, but then Dave is shield-smashed in the face and reels back with a broken and bloody nose. Thag continues staring and doesn't seem to hear Bob)
Bob the Fighter (yelling): Thag! Thag! Do something! Dave needs your help!
(Thag remains motionless, staring. Dave takes a fearsome axe chop in his back and goes down.)
Bob the Fighter (screaming now): THAG! Please, for the love of god, DO SOMETHING!
(Thag apparently doesn't hear Bob and continues staring, holding his temples, veins popping out of his forehead from concentration. Several more moments go by while Bob and Chuck drop three more orcs. The remaining two flee into the woods. Dave is motionless on the ground and apparently dead. Bob approaches Thag.)
Bob the Fighter: Thag, hey Thag.
(There's no response from Thag.)
Bob the Fighter (waving arms): Thag! THAG!
(Thag's concentration is so fearsome that beads of sweat are trickling down his forehead. He doesn't acknowledge Bob. Bob punches Thag.)
Thag: Oh. Oooh. Ouch.
Bob the Fighter: Thag. Snap out of it. It's over.
Thag: It's over?
Bob: Yeah. Thag... about your spells.
Thag: Yeah?
Bob: Nothing happened.
Thag: Nothing happened?
Bob: Right.
Thag: Oh. Well, maybe next time.
Bob: Yeah.
Thag: Yeah.
Bob: It's too bad about Dave, though. Well, let's loot the bodies! Adventure ho!