Sylvannas is so good at pushing lanes and killing creeps with "Unstable Poison" that is the only thing you will need for that job IMO. Since HOTS is mainly focus on team fights it's best to play her with the ability to help get those hero kills.

The Key to playing her is lvl 16 Cold Embrace and having a Wailing Arrow that shuts an entire team down for 5 seconds and if your shadow dagger spreads you should be able to toss a second one shortly. This build will make you a team fight assent and you should have no problem pushing and clearing lanes.