It fits the theme of the set which is being “clairvoyant”, which is having a knowledge about the future or seeing beyond normal perception. This is reflected in the built-in 25% chance for 100% CD reduction for both Reap Spirit and Doom Bolt and, in my opinion, this fits very well to that theme just like the wand proc giving “mental clarity” and energy does.
DB radius is pretty good with the wand modifier and the chance for even more resets on enemy death is a handy feature. Does it help with bosses? Of course not (unless they have adds), but it is a nice tool to use on a monster that is about to die or has low Health so you can get another DB reset and blow up a group.
My Aether/Vitality Cabalist is one of my strongest characters able to take on anything I have tried to kill and I attempted to fill up the AoE need by using the Aether SoC Conduit and Oblivion.
I think the issue here is that you are going for the gimmicky Reap Spirit pseudo-pet amulet that is a trap, in my opinion. RS does not do enough damage as a psuedo-pet skill and is better off maximizing the damage of the skill so you can kill something and get a DB reset.
I do wish that Reap Spirit had a small AoE component so you could hit multiple monsters with each cast, maybe 2 meters or so? That way it’s just small enough to have some impact and get you another DB reset.