Death Strike is only converting one set of Frost/Unholy runes into Death runes. It’s also converting the unused Unholy rune on the first Death Strike.
Should simply convert the used runes to Death runes over and over again but it’s just wonky right now.
Here’s how it should work:
https://youtu.be/cW3oSxoOU-E?t=15
Here’s what’s happening on Beta:
https://i.imgur.com/766vhEL.png