This build is an assassin build with burst dmg, mobility and stealth.
Sylvanas is very deadly early game and late game.

Quick run down.

Tier 1 increase range of Q

Tier 2 Teleport Q is fully stack spam Q.

Tier 3 Teleport or not become stealth for 3 seconds.

Tier 4 Dmg

Tier 5 10% Movement speed per enemy hit with Withering fire, allows you to chase enemies for a long time.

Tier 6 Cast extra Hunting wave after the first one, basically you gain all the effects that you got on the first use of Hunting wave >> Stealth 3sec, Full stack Q(5), and Movement speed per enemy hit with Withering fire.

Tier 7 Deal more dmg to center of arrow, use this to kill enemies that have escaped.

More details about this Hero will be coming soon with this build. (Posted it so you guys can give it a try.)