Honestly, every single heroic character in FFXIV tends to be suicidally optimistic and naive when it comes to walking into villains' traps. Often, it's because of that assumption of good faith you mentioned, as with Ilbred...but sometimes it's because there's a presumption that not falling for the trap would be "unfair" or something. For instance, nobody trusted Asahi as far as they could throw him even before he went Mask Off in front of the WOL, but everybody, including Hien, just walked into his trap. Likewise with Shanti in 4.1, whom they KNEW was Tempered and literally could NOT be acting on good faith as a result of said Tempering, but still let her into the conference at the palace and thus almost got the conference leaders turned into slaves.