Ring of Frost, a Ring of Steel transmuter, converts 100% of piercing damage into cold damage for RoS. Would be nice if it accounted Circle of Slaughter synergy as well by converting bleeding damage into frostburn damage, much like Tainted Power transmuter for AAR converts lightning into vitality.
You can’t convert bleed in general. So it would be kind of weird.
…yeah, bleeding is an oddball. I’ve heard somewhere that devs had some issues with bleeding when migrating damage types from TQ (correct/enlighten me if I’m wrong, please). A pity it couldn’t be made into a proper DoT counterpart to piercing… would’ve made things like damage conversion so much easier code-wise (maybe; I’m not a coder myself).
Pretty sure it was just a hold over from titan quests damage types. Also sucks that aether and chaos damage get shafted on dot conversion.