I do not favor this built, but rather skill blinding wind for hitting more targets (lvl 4) and slowing enemies (lvl 13) -> less enemy focusing (super time saving) as the blinding wind prioritizes Heros over Minions and you can continue pushing or retreating without needing to decide which Hero to shrink (Shrink Ray, lvl 13). Lvl 16: Unless you plan to often get below 50% hp, consider another trait, "Serpent sidekick" (more damage output) oder "Two for One" (more heal, never mind the longer CD, it really is nothing).
Calling this best built is a bit daring, but as always: Builts need to fit the play style! :)