My last word on the Military civics:
I'm not sure the problems have anything to do with positioning in the tech tree. I think they reflect an imbalance in the bonuses themselves. As you say: +25% culture and +2 happy Barracks are primarily flavour bonuses. +100% Great General emergence and -50% upgrade costs are equally powerful. But +2 XP is very strong across all eras while +25% unit production is just "nice to have." (Units don't cost all that many hammers.)
The distribution of these bonuses in your latest proposal is fine. (I would probably swap +2 XP for +25% unit production, but that's about it.) I do think Standing Army should remain at Military Conduct, though. It is rather anachronistic for the Ancient Era, especially as Simon Jester describes it:
Here's my thoughts on each bonus:
+25% culture in all cities: flavour, suits Warrior Code only.
-50% upgrade costs: strong, only makes sense for Standing Army
+100% Great General: strong, makes sense with either civic
+25% unit production: moderately strong, gets weaker the later in game it is, makes more sense with Standing Army (able to mobilize new troops much more effectively)
New units receive +2 experience: strong, makes sense for either civic as both have a strong focus on training and expertise
+2 happiness from Barracks: moderate. Suits either civic though 'Barracks' does seem more appropriate to Standing Army. It's tricky to imagine noble knights/samurai/tarkan/etc stationed in barracks.
You know, the more I think about it the more I feel that the problems I'm having with these two civics are because we moved Standing Army so much later in the tree.
I'm not sure the problems have anything to do with positioning in the tech tree. I think they reflect an imbalance in the bonuses themselves. As you say: +25% culture and +2 happy Barracks are primarily flavour bonuses. +100% Great General emergence and -50% upgrade costs are equally powerful. But +2 XP is very strong across all eras while +25% unit production is just "nice to have." (Units don't cost all that many hammers.)
The distribution of these bonuses in your latest proposal is fine. (I would probably swap +2 XP for +25% unit production, but that's about it.) I do think Standing Army should remain at Military Conduct, though. It is rather anachronistic for the Ancient Era, especially as Simon Jester describes it:
As nations grow large and prosperous, it is natural for them to expand their permanent cadre of armed forces into a continuous, professional organization which is paid for service on much the same basis as civilian employees would be. The rise of a professional military is usually accompanied by the rise of a dedicated bureaucracy or staff, which makes management of manpower and the military-industrial complex more efficient. Easy access into a volunteer military from citizens of all classes also makes the military an organ of social cohesion.