According to description, “Fuel of Anguish” should give 3% base critical strike chance per 100 missing health to “Marrow Shards” if “Marrow Shards” were triggered by “Feast of Bones” node.
With current hp = 100, and 2000 max hp, “Fuel of Anguish” should give ~57% base critical strike chance to “Marrow Shards”. My gear has ~150% increased critical strike chance in total.
So, I should see critical strike every time “Marrow Shards” is triggered by “Feast of Bones”. However, it doesn’t work as expected and most of casts are non-critical hits. Tested on target dummy without critical strike avoidance.