I was just testing it on my mDK yesterday. Noticed the same thing. I was getting consistent hits of 5028 on the trolls in Vvardenfell. I was using a charged inferno staff to ensure burning procs and never had a change in damage from 100% health to 0%. They had burning applied to them the entire time as well.
On PS4/NA, and I thought I just didn't know how to use the skill properly, until I saw this thread. I can say that Frost Pulse works, you do get the Minor Protection buff, but Flame and Shock both appear to not be working as intended.
DDK ist die letzte Verteidigungslinie des Dolchsturz- Bündnisses auf der 30-Tage-No-CP- Kampagne(EU) mit dem Anspruch, in kleinen, anfängerfreundlichen Raid-Gruppen möglichst epische Schlachten auszufechten.
DDK is the Daggerfall Covenant´s last line of defense on the 30 days no-cp campaign (EU). We intend to fight epic battles in small, casual player friendly raid groups.
Extra damage relate to extra damage to burning enemies, not the direct cast itself. It's a garbo execute - at full power it barely does more damage than a whip/force pulse while costing twice as much.
Someone in one of my guilds tested this rather intensively and the bonus damage is a cute semantic trick.
The 300% execute scaling only applies to the extra damage that you do to enemies. It is coded as a separate tick of Direct Damage called Pulsar Afterburn and it does indeed exhibit the promised execute behavior.
At extremely low enemy HP levels you can achieve about ~50% more damage from Flame Pulsar courtesy of the Afterburn tick (e.g. Pulsar hits for 10k and 300% Pulsar Afterburn hits for 5k, making for a 15k total hit).
So, there it is. Its utility seems rather limited to the non-magDKs out there hoping for a universal Magicka execute.
What @YandereGirlfriend wrote is accurate. I disagree only with one thing, it's not a semantic trick, the spell ingame specifically says that execute bonus applies only to the "Additional damage" and not the base one.
Simply explained it works as follows (numbers are only indicative)
1. You hit a target with Fire Pulsar and it gets damage by the Fire Pulsar for let's say 1000 dmg.
2. You hit a burning target with Fire Pulsar which causes the target to take 1000 damage from Fire Pulsar and another 150 damage from a separate attack called Pulsar Afterburn.
3. You hit a 1% hp burning target which will cause it to take 1000 damage from Fire Pulsar and 600 from Pulsar Afterburn (150 increased by 300%).