I remember, we get Mat early, then we get Mat carrying the Dagger(you know the one i mentioned that destroyed an entire city of light that was a constant fighter against the shadow) and that dagger changed his personality, it would have happened to anyone. The fact that he carried it as long as he did is a testament to his character.
But it this version we get a full on character assassination of Mat. You are right that the full blown Mat comes later, but I would say book 3, you know when he got up out of a sick bed after being healed by a full circle of Aes Sedai, and traveled to Tear to save Egwene,Elayne and Nyn from Black Ajah.. but I suppose that doesn't show any strength of character at all...
There are things that are going to be changed, you can't put the entire books into a 8 episode series. It is some of the things they choose to keep that surise me, honestly the whole warder episode it doesn't advance the plot at all, and isnt really necessary(in a book its great, in the series it wasn't need(in imo))
Noone has to agree with me jsut my opinion, and im not saying the series is terrible, but there are some decisions that jsut do not make sense to me