Mulligans
General Mulligans
Keep any 1 drop. Power Word: Feast either with Frazzled Freshman, or on coin with Injured Tol'vir. It has to hit something to be useful.
Dragonmaw Overseer can be kept either with Imprisoned Homunculus or with a 1/2 curve, or even a 1/coin curve.
Sethekk Veilweaver should be kept either with a Frazzled Freshman , or with coin a Power Word: Shield
High Abbess Alura should only be kept with coin if you feel like going for a highroll
Aggro Mulligans
Keep a lower curve, you live by the board, once you lose it you lose
Combo Mulligans
Special mention here, but only keep this if
a) you are 100% certain you are versus a combo deck
b) you aren't mulliganning anything else, as she is normally a pretty dead card till later, so you need a good hand to put pressure on
c) you know how to disrupt your opponent's combo, and when it is at its most vulnerable
basically throw her back and hope to see her right when it would hurt them most