Yeah, I don't get One Man Army's high requirement. It's like they don't want us to test it for the alpha. Or maybe it's more a thematic reason where level 8 is more when the character's true Godwoken power would be released. But I think it's more of a playstyle choice than anything. Level 4 would be a good requirement, though I can't quite remember when you get that second and third talent. I believe it might be level 3 and 6 or something? It's requirement should be on a level where you gain a talent point. Even level 3 would be fine. I could see not wanting it at level 1, just to show new players what it's like to play with companions, nevermind that it would kind of screw up the initial balance a bit where you might not have a full party anyway.
Haven't really checked how One Many Army works. It gives you better stats when you have reduced number of companions that scale up per party size below 4, no? How does it scale up? It's a bit annoying that if you wanted a 3-person party, all three characters would have to take the talent for probably a minimal benefit. Would be kind of nice if it gave the One Man Army talent person an aura or something that benefited your remaining party member(s) so not every character would have to take the talent to have a balanced 2 or 3 character run, but that's not a huge deal really.