Time it takes to become a hero in GA with the different classes

So it is a sketch of what you feel is the time to become a hero, subjective. To create chart, you need data, charts, or graphs are then visualisation of that data.

You could choose a box plot to visualise such data, you could actually do it, though probably pointless, since the expression of your feelings in the sketch is suitable for this environment.

I agree with the BP gain partially, but I must state, that I have played reinforcements instead of the heroes in second and third stage and was basically beating everything and when I died,

I just took another one, since I had plenty of points playing regular troopers.

I have levelled up all the classes to max level, except for hero/villain starfiighters, and I can tell you from personal experience and from what hell I have caused to other players playing jumptrooper, that giving a player like me earning ability on jumptroopers, there is gonna be so many unhappy faces, game would not be balanced, since reinforcements can pretty much melt the heroes and are considerably cheaper, manoeuvrable and more powerful than any other unit. Their downside is their health and regen, but you can manage it with star cards, all three actually.

To sum up the reinforcements, they are perfectly balanced, as all things should be... snap.

 Regarding the AT ST, have a look at Crait or Takodana for example. On these maps, you can see how quickly speeders or fighters, respectively, can melt the ATST with the player in ATST barely earning for a new one, keeping his score high, but his BP low, near zero... I can also tell you this from experience, that before they nerfed tanks, you could earn up to 60k BP on Crait in the first stage and now you can barely earn 10k in the first stage, if at least one enemy is using their speeder to attack you, and it takes one speeder, one run and ATST is no more.

Every map has this, one counter vehicle, one run, one kill.

Cheers.