The only drawback is that it wont last for long at the early game, but it is a huge card at mid late games, and at turn 3 or 4 it can slow down an aggro deck
Channeler, in my mind, is at the top of the list behind Scavenging Ooze and Chevill
Also, the Ditto at the beginning of Pikachu's Ghost Carnival , in which the Ditto gets circling stars when it got hit on the head by a Cubone while Ditto was disguised as a Cubone
Vilis' activated ability also draws you at least two cards any time you use it, as you'll pay 2 life to use it
A single sought-after card almost always earns more on its own than buried in a bulk lot, where buyers expect a discount
She gives all Squirrels menace, makes squirrels when you sacrifice food, and can buff all your squirrels by Foraging