Except none of those are having 2 different personalities and is consistent to their character.
Alistair never hides his hate toward Loghain.
Morrigan doesn't hide she is manipulative in fact she even told you she is.
Needless to say you show great bias toward her to the point you try paint not leaving the warden as why she is best Li , but fact is she leaves you like Alistair and even tries to kill you if you upset her and leaves you after dao.
Alistair is a living oxymoron far worse than Leliana and will be fine and follow us if we :
kill Connor or Isolde, Wipe out the Circle , Preserve the Anvil where Dwarven souls will be forged into Golems, Kill the Dalish Elves. Or the Werewolves, Leave Redcliffe to the zombie horde, sell Elves into slavery (which would give us no reason to condemn Loghain), work with a possessed corpse at one point and murderknife people left and right
He seem like a child who has no concept of where he stands on anything,that he is more willing to accept slavery and follow the Warden rather then work with Loghain makes me really see him as a fool with triple personalities
Morrigan is far more naive than leliana what kind of manipulator would like to reveal so openly that is a manipulator? 
Leliana is simply faith unfaithful kept falsely true