This character was very logical and didn't display his true feelings. Even Dumbledore misunderstood Snape's feelings in 1997, and by then Snape had worked for Dumbledore for more than a decade and a half. Snape was also introverted, so Dominant Ti and Inferior Fe makes sense.
Snape was very inventive with spells when he wrote in the Half-Blood Prince book. He invented many new spells, and wrote them on almost all pages of the book. He also had an excellent sensory memory, and was able to tell what was wrong with a potion simply by sensing it. Auxiliary Ne and Tertiary Si.
My vote goes to INTP.
What do the rest of you think?