I would suggest that you stop thinking about what the FBW is doing and just fly the aircraft. The Airbus is trajectory stable, but effectively all this means is that if you're displaced from your original trajectory (eg an updraft) you'll keep flying the same 3 degree slope, but too high. Instinct suggests to me that if you're struggling to follow the flight directors, you might be making inputs that are too large.
Do it right on the Airbus and the flight directors will follow you, not the other way around. Don't forget that you have the ILS available for reference.