I have a suggestion: if players don't like to build certain unit or building, or use certain trait or promotion, it's probably a good idea to improve them HUGELY, not just a tiny bit. For example, protective trait may actually good enough now, but in my perception, it's still weak and unattractive. After all, it's perception of balance in player's mind that's really matters. We can always tune down them in the future if we went too far, but then the player's perception will have already changed.
It's funny you say that actually, because I already am a bit of a fan of the Protective trait in the original game, and the boosts I've given it make me feel it might be too powerful now. Consider that Pro leaders are more likely to be able to make early use of the Drill 3 promo and the drill promotion line has received the boost relative to combat promos.
I know what you mean about making big changes, but I'd rather stay on the safe side and make small changes and then re-adjust if it is decided it still isn't enough. After all, most people don't complain the original game is horribly unbalanced.