I wasn't able to understand the majority of your post, but here is what I gleaned from it.
First of all, you are assuming we are playing with a 4k setting. Most people play in 1k, which means your point about them being powerful economically doesn't stand here, as you cannot recruit Thorin on a 1k start.
Second, Ered Luin is supposed to be a hero-centric faction, thats why they have so many heroes. The other factions focus more on their troops.
Third, right now Ered Luin is broken and much more powerful than any other faction in the game. That is why people always pick them