Irda Ranger said:
Just make the rest of that crap up. Who cares how may ranks in Profession (Juggler) he has? Just give him whatever you feel he needs to make him fit into you worldbuilding plans. That's what I've done for years and as long as it doesn't screw up the CR it works perfectly.
So, basically, he's as good at everything as any other monster of his level is. He has no special powers to help him fulfill his role *in hell*, just his role as an opponent for the PCs. He has a bland, boring, list of a great big THREE skills. He has no mechanical existence outside his combat role. He appears to fight the PCs, then he's done. Everything about him is centered on his existence in the encounter. (I mean, he doesn't even have Planes knowledge!) ("So, Pit-dude...where do you live?" "I dunno. Don't have that skill. Let's rumble!")
His one bit of interesting text -- the once-a-century-wish -- seems to be almost an afterthought. Why once a century? Presumably, he's not going to be granting wishes to PCs, so it's not much of a balancing mechanism. To reduce the total wishes available in the world? I dunno. Further, since there's no way (other than DM fiat) to determine if a particular Pit Fiend has already granted a wish, the century limit is kind of 'Meh'. I suppose it has some kind of mythic resonance, and 4e does need all it can get at this point.
Yes, I can "just make it up". Which leads me to ask why I'm buying a Monster Manual...or a rules set...when the kneejerk response to every complaint about missing or oversimplified information is "Dude, just make it up!"
I can make up the whole game if I had to. But I was under the apparently silly and mistaken impression WOTC wanted my money and was presumably going to sell me more than a blank sheet of paper labeled "Make it up".
(And in the Great Painful Irony department, the part we SHOULD make up -- the world -- is being spoon fed to us. Sigh.)