Sacrificial Steel slot is flexible for:

• North Wind - cold has bonus against shields (+50%) and alloy armor (+25%). Slightly lower average damage than sac steel but made up for by bonus against specific enemies
• Weeping wounds - boosting status to 100% allows you to proc corrosive which reduces armor and might help with subsequent hits. Note: it is difficult to exactly calculate if [Weeping Wounds] surpasses the other options as it depends on the enemies armor level and number of corrosive procs. In general it probably scales higher against high level grineer/corrupted armor, but at this point you would run the hybrid slash build which definitely uses weeping wounds.

For Corpus - swap [Shocking Touch] to [Virulent Scourge] to make pure toxin.

Desirable riven stats:
Positives: Crit Damage > Damage > Crit Chance > Elements (toxin, electric, cold preferred) > Combo duration
Negatives : anything that isnt above