I disagree with many here...
Phione in my eyes is a legendary Pokemon, yes stats are below mediorce, you can get it countless times...but that doesn't deture it's label from gamefreak as 'legendary'. Though those are fine ways to label a legend. As many of the uber tier, are legendary.
Though think about it, Manaphy IS legendary, even in the Pokemon dot com mailbag they confirm that, along with rotom not being legendary, anyways...manaphy is legendary so how can it's offspring not be, for your information, YOU look like your parents, have traits of them and probably are in some cass exactly like them in ways...
I am of the opinion that Phione is not a 'child' of Manaphy, more a genetic fault. Ditto fails to copy Manaphy's genes right so a crossbreed is created. Also Phione is taller and heavier than Manaphy so this ruins the 'child' theory in my opinion.
Phione doesn't have that power, that folk lore story...yet its parent, is legendary, picture this. Manaphy in the sea to it's legendary palace "home". phione is with it, and say we lived in a Pokemon world for a minute. Say you cuaght a phione, as a fisher when are you just going to go "meh, it's a phione". (like a magikarp) no! your going to be excited that you got a phione that would be rare in the pokemon world and comes from a legend.
It does not actually appear in a legend and feebas is also rare, but is it legendary?
Remember folks, we ARE in a pokemon world, we're in the game... I think all this "oh its stats are low" is a bunch of you know. In the perpective of you playing a video game your looking at it wrong. Take the perpective of it in the world. You think you'll see a bagillion phione in the sea, No. Phione to me, is classified as a legend to it's rarity IN WORLD perpective. I believe if the parent is legend, so is the child, as the child CAME from the parent, thus being it's status. Phione is depicted as an angel in the sea, are angels to you common and normal like everyone else? I dont think so...
In the battle real world perpective, phione is banned from the sinnoh battle tower, hmmmm....think of that?
But alas, just my opinion...great discussion, thank you for making this thread. I enjoyed it.
This is also just my opinion
So you know, we could create an in-between zone, over normal under 'perfect' legendary, idk just a thought....