Please no.
Many folks have beat the game solo.
I've just finished a no long rest, no barrelmancy play through with a party of 2. (And then another no long rest no barrelmancy play through with 4 Wizards)
Players are plenty strong.
The last thing this game needs is a bigger party or more damage output.
It would make combat trivial.
I'm sure Larian will include a story mode for folks who don't want the combat to be challenging.
How can you play with 4 wizards ? There is Gale and yourself. Where do the the other 2 come from ?
And how do these wizards recover spells and survive without long rests. I assume you start from level 1, right ?
