Can you elaborate on your experience with balancing, snowram?
I participated quite a bit in the development of a relatively popular Cube World clone. Balancing was already a hard process of trial and error, but accounting for party size was downright hellish. Numbers aren't growing linearly, they follow weird exponential functions where you have to consider dozens of variables. How much damage should both parties do and take, how many enemies should there be, how AoE, buffs, debuffs and crowd control interact with more enemies, how fight readability changes with more characters, how the environment fit for the number of characters... And considering we are talking about a CRPG there, I wouldn't risk my sanity.