For what it's worth, I think that word has been established to be truly unpronounceable... the written word is some pale approximation of some arcane Ehlnofex incantation (figuratively speaking). As for Dee-dra vs. Day-dra, I say Day-dra, but some of the VO in Oblivion pronounces it Dee-dra... probably a regionalism. Interestingly, the only real-word correct pronunciation of that syllable would be a long I, as in buy, but hey :shrug:
I say VI-vek, short i, emphasis on the first syllable. I've said it that way since I bought Redguard (whose included Pocket Guide to the Empire kicked off my fascination with the Tribunal), and I don't care if the ALMSIVI themselves say it differently.
Also, I've always pronounced Khajiit as ka-ZHEET, but (and this MAY have been a dream, because I'm weird) I thought I heard an in-game voice say KA-jit. It made me shiver. It made me feel the way I feel when people pronounce crepe as kraqe. It was that bad, and it's not even real :ahhh:
And, dreugh... ummm... a wizard did it.