Ok i see leveling up trough fights vs story progression is a debate itself and i really appreciate motivations pro the latter.
My main observation was and is that 1) we are maxed up ad around 60% of the game and 2) in my experience level 7 to 12 was too fast to experience each new abilities i just gained and totally had no time to become accustomed that i already leveled up again.
We shoul all agree that abilities you get on level up are things you use during fights so if you level up mostly thanks to dialogues and plot xp you as a player will not really experience what being a level 10 or 11 (insert class here) means, unless you encounter fights during it. This happened to me. So those non fight events back to back should be less impacting on xp or be interspersed with more fights.
I think developers should look at the ratio between fights and story progression you encounter along the game and keep it armonic.

Hodo observation: "level 4 to 8 is too slow". I didn't notice this, i indeed liked the pace at that point: each level seemed a endless chapter on its own and i felt the struggle to push it back and the joy to discover the next. This is subjective. What is objective is that there are 12 levels so they shouls divide the playtrough in 12 and give the player 12 layers of complexity, 12 chapters. As it is now the last is disproportioned.
I think in a way or another this is easy to tune.