If you are killed by only the damage from Luden's Echo (just the item damage and not the associated ability), the Death Recap shows that you were killed by the ability itself and does not list the item as a damage source.
-Fyzzx
Yep. Got killed by "Primordial Burst" 
... 300 damage, lel.
Oh I wish it was only that...
Death Recap is currently a mess. The whole thing needs redone.
Only time I ever look at it is if I'm a tank an want to see what type of damage is killing me the most so I can plan my next build. But often you don't need this anyway. And even then 90% of the time I see the source of about 30-40% of the damage I took. Which isn't enough information to go on.
This is why your other replies may seem silly. It's a known problem.
