Not sure if this is a bug or not, but it's completely unfair.
There is a winter duty officer assignment at Qo'nos called "Test effectiveness of adaptive outerwear designed for Gorn". It requires 2 doffs and has no traits listed whatsoever, neither good nor bad. No matter what rarity of doffs I use the critical success won't increase and the chance to fail won't decrease.
Screenshot of KDF:
http://imageshack.us/a/img9/7449/kdf...assignment.jpg
The Federation side has a very similar doff assignment at ESD that has good and bad traits listed and also the chance to succeed can actually be increased. Edit: I just noticed, for the Fed version the chance for success doesn't increase. The chance to fail decreases and the chance for Critical goes up.
Screenshot of Fed:
http://imageshack.us/a/img24/6181/fe...assignment.jpg
Edit: Proof that the doff assignment can NOT have the failure rate lowered or the critical increased. Selecting 2 blue quality doffs and the failure/success/critical rates are completely unchanged.
http://imageshack.us/a/img267/7449/k...assignment.jpg
*It is somewhat common for doff assignments not to have a requirement that increases the chance to succeed but you can still increase the critical chance and lower the failure rate, or increase the disaster/failure rate if you use a doff with the traits listed. (Example would be "Success: Biologist" or a trait like "Success: Cunning" missing from the doff slots for the assignment)
Edited for clarity.
I consulted the wisest tribble because I couldn't remember where I parked, but all he said was "Jim Carrey slumbers in the hall next to the hidden treasure".