Yeah, I have to agree that the 4 player party is not good.
I forgot how many companions BG2 had -- 13? 14? Much of the replay value came from mixing and matching parties. One party for maximum dialogue options, power party . . . can I beat the game with the hopelessly weak party? I'm hoping that Larian has more than one unannounced companion up their sleve.
I'll be honest, as someone who has put a ridiculous number of hours into the older games... I really don't like having a full party. Even when I do take a full party, I usually end up with at least one person I dedicate as a spare inventory and buff bot.