Eliminate discoverer, give its expos formula to collector and general (or none).
+10% extra planets and -25% research to Collectors.
75% loot inactive and extra phalanx to Generals.
Remove the +2 expo slots.
The reason is simple. This should be a meritocratic game, it is not normal that i can register in a very old uni, with top 1 over 1 milion points, choice discoverer and get a ridiculous amount of resources via expos, while i'm green, just building cargos in a row.
And it is even worse that this way i may surpass a player that took months/years to get his resources building mines. While i can do things without upgrading them.
On top of that, this system allow a 10.000+ rank to get those resources and still stay green. This way it may be used to push "people" via "inactivity", or things like this.
Remove that class and let people chioce only beetween pve and pvp, both with very good benefit.
I want even to suggest to rework the way expos works. The fact that you have only to send cargos and wait, hoping for "luck", is not a good thing. You may think something better, something at least interactive.
Ps: I told you about marketplace and classes. But don't surrender, we can balance them more. Let's keep going!