I personally value Grace and PtW higher than Shadow covenant. But it doesn't deny that there are cases where those are inferior. Given the persons above case:
PW:R -> penance = 750 + 304*3 + 304 per person with atonement prior to starting this sequence
3x Shadow Covenant = 4125 + 0 per person with atonement prior to starting this sequence
Which means you need to have had 8.1 atonements already out for PW:R->Penance to heal more than 3x Shadow Covenant