I loved the 6 party system in the Infinity games. It really felt like you were going on an adventure. Any less than 5 & it was less epic. This is probably why Divinity:OS fell flat for me. Any more than 6 members was too much for combat & you didn't have to carefully choose your party because all your bases were covered (Ultima, Wizardry, etc.) 5 felt good in MMOs.