Well - as the title says, since One Tamriel I've found that using Obsidian Shard doesn't always work and I'll explain how:
It will always hit and do the base damage - no issues there.
The first problem is that often the stun proc. doesn't occur and enemies will still come running at me.
The second problem is that it will not always give me health even if I'm the only person in the area - there are times I spam it and I don't get a single bit of health back.
As a squishy mage I rely heavily on this power to keep distance between enemies - and as a method of keeping my measly 15k health topped up.
Very rarely both of these issues will occur simultaneously, leading to death - that said, it is usually "one or the other."
Please look into this, it's one of my favourite abilities since launch and it's sad to see it not working properly.
PSN ID (NA only): Lagrue
Main Characters: Champion 806:
<Occula Moltenstar> (Fire/Healing Mage)
<Iceveil Thornfist> (Ice/Nature Mage)
<Mistsister> (Lightning/Summoning Mage)
*GRAND MASTER CRAFTER*
"You must defeat me every time. I need defeat you only once"