People did the math and even executing your normal rotation perfectly and using LD on cooldown you would have max 15 minutes of fight before running dry.
There isn't any encounter in the game I've done where I'm fighting for 15 minutes straight with zero downtime.

LD is meant as a tool to help recover if you need to use VerRaises or VerCures or if you're getting raised yourself. It hasn't meant to be a mandatory part of the rotation
Says who?