Even though you can get multiple Phione in a game and that it requires and non-legendary Pokemon, Ditto I still think it is legendary because you need Manaphy to obtain it which is a legendary Pokemon and that it is banned from things such as the Battle Frontier like most other legendary Pokemon are. Also its place in the Pokedex is with the other Sinnoh legendaries. I know the Dratini and Larvitar lines are in between legendary Pokemon but they haven't done it that it in ages putting normal Pokemon in between legendaries. The only other exception of a legendary Pokemon not being in the Pokedex with the other legendaries is Victini but we all know that Victini is officially a legendary Pokemon. I rest my case.