No, that's not vivi. Vivi is always cool
I wish I could play with all these characters, even Blank and Marcus (let's hope Square makes a Final Fantasy IX-2 in the near future), but I used mostly Zidane, Vivi, Steiner and Garnet (in this order, actually, so Zidane helps Vivi by encouraging him, Vivi helps Steiner with his wisdom and Black Magic, and Steiner protects Garnet from monsters and Zidane, of course).
Zidane and Steiner for their physical strenght, Vivi for his deadly Black Magic and Garnet for her gentle (for her allies) White Magic and specially the Summons (the later two for their magical strenght, if you will).
I also used Quina and Freya on occasion. I like Eiko as a chracter, but not to play with her, and Amarant has a strange design (but I played with him sometimes). The ones that can't be missing are Garnet and Steiner, though.
Final Fantasy IX-2 does not even sound or look right.