The general impression I got with the Heroes in Endless Space 2 is similar to the lore of Heroes in Endless Legend. That is, what makes them "heroes" isn't always something fantastic or Dust-related inherently. Rather they're individuals from different societies who for one reason or another got cut off or were alienated in some way by their home world and are now in a position of deciding between reconciling this difference and tentatively rejoining their society or taking their own path. Many Heroes of the Academy in ES2 I get the impression are more loyal to each other than they are even to their employers. (not to the point they'd collude because at the end of the day they are professionals)

A great example of this is the Oroyo Ner Freed, a Craver hero. A rather mysterious one, in fact, considering how much she keeps to herself.

But her political affiliation should immediately raise eyebrows: Pacifist.  A pacifist Craver, in-universe. Just try to imagine taking her on as a hero while playing another faction and then finding out your Pacifist party representative in your Senate is a freaking Craver.  Bet that caught someone by surprise by now.

So why aren't there heroes everywhere if extraordinary circumstances create them? Because only extraordinary people make it through extraordinary circumstances. They're the ones who go on to become leaders, visionaries, people who shape culture and society. That's what it means to be a "Hero" in this universe and even in real life. And considering the trauma and trials that one goes through to wind up in a situation where one has no choice but to become exceptional... well, that isn't something most of us would much enjoy enduring, even if it means transcending our limits.   (A great young adult story about just this kind of thing is Jonathan Livingston Seagull, I highly recommend it)

In a sense though, heroes ARE everywhere, esp. in games with a large number of present empires. 

[spoiler] Emperor Zelevas in the final cutscene of the United Empire/Mezari/Sheredyn is shown as that they use Dust to become him inmortal (Seems like He gets younger with no more white hair,etc...) So not all Dust enhanced are heroes, He is "Dust enhanced" just to become the ultimate inmortal leader for his faction. [/spoiler]

P.D: I know spoilers brackets don't work but wanted put the warning xD

Slowhands wrote:

As far as Zelevas goes, he is not really wielding the Dust himself the way a Hero would--he is more the recipient of a process that uses Dust, developed by Empire scientists to prolong his life and strengthen him. I suppose one could argue that he has the will and the strength to become a Hero, but Zelevas is having waaaaaay more fun running the Empire...

Well... That makes him no different to the heroes that become governors xD It makes Zelevas better because will live longer! that such governors haha (Or heroes are close to inmortal too, I'm not sure)