Belive it or not "Tee-dus is a lot closer to the correct pronanciation than "Tie-dus". The correct pronounciation is actually "Tee-dah", I realize that doesn't make sense, but Japanese is not English, so pronounciations are different. In Kingdom of Hearts he is called "Tee-dus" because Square knew that we wouldn't get "Tee-Dah", it is the same as making "Cefca" "Kefka" in FFVI - in English phonetics "Cefca" would have a different pronouncation to "Kefka"...