Yin isn't a ranger? And I haven't tried a Siphon/Lifesteal build. Just straight power.
I find it weird that her gimmick is supposed to be projectile reflection, but it's absolute shit. I don't think I've used it more than three times a match. Her ult is pretty lackluster too. But her RMB range/damage buff is god-like. Such a low mana cost with that much power should not exist.
I don't run any points in Deflect until the very last four levels. Maximize Windcarver(?) and her Leap for some SERIOUSSSSS damage, especially in a Power and Melee Speed build.