I was playing non-soulconduit setup just before and noticed i was not getting any refunds via the soulsnatcher perk.
This let to me testing the refunds over a relatively small sample size of 50, making sure immolate was not on target dummy when casts occurred.
I only had 6 refunds occur over the 50 casts (12%).
Update: 7 over 100 casts - max streak 30 casts no shard.
So this leads me to ask if anyone has experienced such an issue themselves or could help test further.
Talents: Backdraft, Reverse Entropy, Demon Skin, Eradication, Dark Pact, Grimoire of Sacrifice, Wreak Havoc.
Relics: Soulsnatcher, Immolate dmg, Soulsnatcher
Armory:
http://us.battle.net/wow/character/frostmourne/Iribela/
Of course this could be just a small sample size but worth checking.