When playing Vivian note that you can cancel your shield, I see lower level players keep it up when they aren't using it which means they have to wait longer to be able to use it again.

Buy wrecker, and u will destroy that shield she is very weak without it

Vivian's shield only protects in front of her, use a flank champion such as Skye to attack her from behind. With any champion you should still try to attack her if doesn't notice you.