If it does come down to one on one, I think the prophet could win. Depends if Ikoral gets his Chosen or not, I guess.
A few days too late... but we could resume the discussion. In general, things look like Ikoral is winning. But the Prophet of Vodal has some devastating Force powers ("chrushing affliction" and "soul rend"). If Ikoral isn't shielded or healed by someone else, I think the Prophet could defeat/kill him in a one-on-one (if it happens in the burial chamber).