The addition of Harbinger wasn't very well received, though that mostly has to do with the overabundance of the various scraps and pennies that you would just collect after an awfully slow spawning of mobs, which was improved as the league went on. We are excited to let you know that thanks to our hot sale, we are the best and cheapest place to buy POE Currency Trade online. Finally, Buying From Professional Seller -

Though, with the exit of Harbinger the ease of Atlas progression went away, the upgrades and sustain were noticeably lacking in comparison to it, and even though Abysses kind of remedied that through spawning extra monsters as well, the Horizon and Harbinger orbs disappearing from trade leagues was there, slowing down progression by a decent margin.

While Harbinger orbs made the sustain of Guardian (T16) maps ridiculously easy, Horizon orbs felt like they perfectly served their purpose in giving players that extra little bit of edge while progressing which was, in my opinion, the best part about Harbinger.

The Horizon orbs would remedy a part of that unforgiving randomness with Atlas progression, as it's infuriating to run the same map over and over again, while getting the higher tier map of what you already had unlocked previously, instead of what you needed to progress. It's infuriating to get the same map continuously without making progress.

What's the point of this long wall of text? Well, my suggestion is that the Horizon orbs be incorporated into the core game, just like Orb of Annulments, at a drop rate that doesn't make the orbs too common nor too rare, something similar or even a tiny bit more rare than a Vaal Orb.