I have been playing her all morning and have had some amazing results.
The main points of this guide are.
Shyvana does not work as a tank and must be played as an aoe nuker. Her skills are perfect for this role.
Secondly, Shyvana does not need to build anything other than attack damage. her skills have low cooldowns and are spammable. She is very similar to a completely melle gragas.
The main point which i should say thoush is that Shyvana is a whore.