In my study and observation of type, I have seen a number of cases which are fundamentally confusing and get in the way of my nice mental representation of how things should be based on the theory.
The most frequent of these cases, for me, lies in the identification of a Te-base vs an Fe-base, especially when paired with Creative Ni. These people are often highly dynamic - especially those who are comfortable with their Se - and do not give off a consistent vibe of any sort by which I can judge them. It is almost as if they are capable of using both Fe and Te in droves - managing to somehow derive both their logic and ethics in an object-oriented fashion.
The way in which I have currently reconciled this is by Jung's original definitions: An individual is characterized most by an overall attitude of extraversion or an overall attitude of introversion, so an EN-j type may in certain contexts appear to use both T and F in an extraverted manner. This is a messy conclusion, though, and still doesn't lock them down.
I'd rather not be too specific, as this refers to an amalgam of personalities with different aspects of both Te and Fe. Bear in mind, however, that all of these individuals have a number of characteristics of Lead Fe and Te as well as Role Fe and Te. Their behaviors also highly correspond to both the ENTj and ENFj profiles, but not to any other profiles in general.
How would you go about differentiating the two? What questions would you ask yourself in the process?