This is something you do AFTER the initial agro burst. If you do it right you still have 55-60% after everything. My tank friend does this on small pulls to because he's so used to the rotation. You think it doesn't help much because of rng, but add that then stunlocking from holy basically makes you almost as invincible as the hallowed + holy spam combo for 17 seconds of 0 damage being done to the tank.
