Harbinger used to be one of the least succesful/recognised Heroes, both in competitive and pub matches, and his innate passiveness was mostly to blame. His powerful lane control could earn him a place in the mid lane, from where he could hopefully snowball. However, even this was a best case scenario, for a lot of reasons:
- Lane control was pretty much all he had. Even after a good start, his level dependance and long cooldown ulti didn’t allow him to be as active as a solo mid Hero should be.
- There were quite a few counter picks, so even his laning could be overcome. Opponents like Razor, Viper or Kunkka could pose a serious threat, taking away his only redeeming quality.
- Despite being a damage dealer, he couldn’t apply his damage on spell immune units, namely buildings and BKBed Heroes. He still has this last one, and we’ll come back to it later.
With these in mind, the traits of Arcane Orb and Astral Imprisonment have been swapped a bit. His Int steal being now part of his Orb allows him to be a more active character earlier on, while one level in Astral still lasts 4 seconds, making for an effective control skill.
Whether his lane control is a bit weaker now is questionable. I believe it depends entirely on the matchup; the old Astral would destroy an opposing Int Hero, but it wasn’t as good versus others. The new Orb is powerful against most matchups, but more expensive in terms of manacost. In the end, it comes down to some good Essence Aura procs, RNG bless us.
He’s now picked in pubs quite often, and with very good success rates at that. In competitive matches, not so much as some would expect, but he’s still definitely a valid option.
And now that the technicalities are out of the way, onward to the question everyone wants to ask.
Is he broken?
A lot of people would argue that he is, but I’ll have to insist, he isn’t.
What I mentioned before, being a DPS Hero who doesn’t apply his damage on structures and BKBs, is a huge weakness.
Don’t forget, kills mean nothing, throne means everything (!) And our buddy Harbinger is all about kills. Sure, it’s a way to go about it, but even 5 seconds of being unable to damage the enemy can be a lot, not to mention 30k net worth items, which translate into minimal tower damage.
This is why he got buffed again and again in 6.86b and c, and still isn’t that game breaking. Even in pubs, people will find ways to counter him eventually, and he’s nowhere near the pubstomps of Trolls, Snipers and Ponies we experienced last year, and  Wizards we’re still experiencing now (I’m looking at YOU, Invoker you lousy witch) .
I believe he’s fine the way he’s now. He’s a valid pick, he can carry, and he can fail, he has strengths, he has counters (nyxnyxnyxnyxnyx!). Of course, tweaks will always be needed, the meta changes, new items are added at alarming rates, but I would approve our new Devourer.