Big Priest Wild March 19 2019 patch version 13.4

At almost all situations you want to mulligan your hand so you can get BARNES (if not in first hand) so at turn 4 you can summon a 1/1 token of a minion n your deck (if lucky Y'SHAARJ) and kill it so you can revive it with cards like RESSURECT/ETERNAL SHADOW and have a full stat big minion in your board. If  BARNES is not in your first hand then you will have to survive until you can play your big minions and try to clear the opponents board as often as you can by controlling the game with AoE(Area of Control)  cards and removals.

In AGGRO Decks you want a second scream from SHADOW VISION if possible so you can clear the board from your opponents minions.

In Paladin decks the best time to use scream is when your opponent have lot of silver hand recruit so he has useless 1/1 crds in his deck