I've never found IEIs that difficult to VI, occasionally an Fe-sub (more commonly the 3s) can have Se-like qualities, or be closer to an Fe-dominant; but on the whole, there's always the same casual aloofness, appropriate degree of emotion withheld, lazy composure and sunken focus. Ni-subs have a soft self-containment, like you know they're there but can't find their exact locus, whereas Fe-subs have more of an emotive overtness, and give off a sense of communicating things just implicitly enough. sorry if those sound vague, I haven't thought about socionics in a while...