I find that Guardian Soul harvesting is very missable. With all the end-raid screen spam happening + environment effects like a snowy ground or a lava pit, it is much too easy to miss seeing it.
I think a large pillar of light (similar to the EPIC gear pick ups on the ground) should accompany the soul pick ups.
Or even have it be something your pet can auto-pick up since regardless of picking up the soul or not your daily harvest is burned if you checked off “harvest guardian soul”