Mulligans
General Mulligans
All of These Cards are universally good so try to Get them but some Like the Knife Juggler are so susceptible to backstab, Fiery War Axe, Frostbolt that it might be slightly worse against them.
Aggro Mulligans
All of these cards are very good at killing 1 health minions zombie chow is an all star here as you are trying to push the game late.
To Note:
It is correct to use your heal spells (Flash heal, Light of the Naaru) on yourself without Auchenai Soulpriest .
and
notice the exclusion of shadow bomber normally this card is great but against other aggro decks yours is slower so the bomber hurts you more than your opponent.
Midrange Mulligans
You are looking for your value cards here, you want cards that have the maximimum impact on the board while still maintaing aggression which is why cards like Spawn of Shadows, Forbidden Shaping and of course Auchenai Soulpriest are so good.