Viviana in my opinion, is a mediocore Story Character, who requires some real planning to play properly. For a Force, her TP stats is poor, and although her ability Bonus TP is all fine, it's easy to put stumbling blocks in her way.

The key to being a powerful Viviana user is tied into your EX bonus. You need to raise your EX bonus to at least 2 for it to be of any real use, better would be 3, which is pretty hard to do, which means your deck has to be tailored to gaining a decent EX bonus.

Items:
Elysion x1
Club of Laconium x2
Windmill x1
Summit Moon x1
Rabbit Wand x1
Fatsia x1
Storm Wand: Indra x1
The Sigh of a God x1

Action:
Foie x2
Zonde x2
Gizonde x2
Gibarta x2
Rabarta x1
Guard x2
Cane Guard x1
Punch Guard x1
Resist x1
TP Attack x2

Assist:
Cane Palace x2
Dice Fever x1
Reqieum x1
Charity x1

While this deck has less weapons, you're only looking to attack twice per turn early on, Viviana's power only shows later in the battle, once you have that EX bonus. Several of her weapons will allow her to do some decent damage with normal attacks, especially if you use the TP attack action card. The assist cards in the deck are mainly geared to gaining you EX towards your bonus, except for Cane Palace, which will either give you some extra 'oomph' early on, or just make your techs absurdly powerful later on.