Some people have stated that on NG+, persuades have had all around
higher requirements. The reason for this, be it NG+, player level, or
whatever else is not important. The apparent fact is that something
makes the persuade checks more difficult on subsequent runthroughs.
Kim Stolz wrote...
Those are some of the hardest persuades in the game.So unfortunately for some people they aren't going to be able to get them without being completely renegade or completely paragon. Now, trying not to spoil anything for anyone, some persuades are easier if you go paragon and some are easier if you go renegade. This was done on purpose story wise so people would have different experiances as they played. They are possible to do just very difficult.
Perhaps, with the NG+ persuasion difficulty, the Tali/Legion argument is
only capable of being resolved with the Paragon option while the Miranda/Jack argument is
only capable of being resolved with the Renegade option. This would fit with what people have been saying, and it makes sense according to the dev post.