Okay, last one for now, I swear. I've been saving them up!
Okay, just re-ran Carnival for the first time in a while and I gotta say, it seems wrong for devils and tieflings to be in level 5 content. It seems wholly inappropriate. It is just way to low of a level for those sorts of enemies to be appearing. Personally it rips me right out of my suspension of disbelief when incongruities like that crop up (similar problem with Chronoscope, and, to a lesser degree, VoN6.)
This isn't the (why-the-hell-are-there-rats-in-this-level-17-quest) thing, which results from lacking an infinite budget This is simply an impression that you took what is a fairly neat series and just plonked it down where the release schedule said you needed more content. No one should be seeing such enemies (evil outsiders) in any sort of number until at least level 9.
While I know it is highly unlikely, I would really suggest that whole pack get revamped into a level more appropriate to the content. It has cool stuff in it and a lot of it is really excellent. It is just wrong at level 5.
Maybe it is just me, but that sort of thing is the same issue I have with epic. (Level 25 zombies, even *pirate* zombies, is just wrong.)