Love your feedback! Thanks for the time spent on testing and writing. A few comments:
GAMEPLAY
2) At the beginning of the game, I felt cantrips were strong but later, especially in the underdark, raw damages were so ridiculous
This is kind of by design. When you are low level without many spells, you are not twiddling your thumbs when you use them all. As you get more powerful, they are needed less (except warlock - again by design)
3) I noticed I rarely wanted to use buffs
I use them all the time. To me, trading x damage now for 2x or 3x damage in the future is worth it.
3) Can we have Alfira as a bard companion, please ?
YES YES YES PLEASE PLEASE PLEASE! LoL
I love buffs but I feel sad when the enemy instantly breaks my character's concentration

what do you do ? do you buff with forced turn-based mode and trigger the fight ?