mulligan for malchezar imps, soularium, darkshire libraruim, expired merchant and howlfiend. look for shriek to if you know you are against aggro.

you can also keep  specific openers like high preistess, quest and a soulfire to start handfilling faster.

the best opener will be malchezars imp + soularium on turn 2 due to it being draw 6 discrd 3.

dont be afraid to discard your heavy end cards like malganis or bloodreaver due to not needing them to win.

when the meta is slower and fatigue matches are more common, sub out the cataclysm for an archivist elysiana.

try to make the soul infusions land on high priestess, due to her keeping the buff when discarded 

Ive hit rank 5 with this deck so its not quite legend tier, but it can deffinitelty take games of tier 1 decks due to insane card draw and playing the quest reward turn 5 or 6 typically