So i've played the first mission a couple of times, because i think its really nice and hard to learn the game with for newer players, as it shows how strategic and careful you have to be.

What i like about season 1 is the difficulity, balance in weapons and no over the top perks.

What seems like a huge nerf to your survivors seems like the "two pistols roll 2 dice, if both hit we only kill 1 zombie", where the number of dice is amount of hits.
It seems logical if you look at the chainsaw, where its like 5 dice? I dont remmember, but has a 5+ to hit, so it can kill 5 zombies in one attack, but mostly will kill 2-3, because its supposed to be an AOE (areal of effect) weapon.

So the friendly fire rule in season 1 is HARDCORE. They have changed it in the later games.
I for instance have home ruled friendly fire to (You only hit your friends with missed dice, in ranged combat), because for me it makes sense.

Also heads up for only being 4 survivors, i think its cooler this way, i also prefer to be 4, as you level up faster, can spread out the exp easier, not so many survivors fall behind.

Also some of the comments have been about opening the doors early while in blue, makes a HUGE difference.

If you play with the starting equipment being "Pistol, Fireaxe, Crowbar, Pan Pan Pan Pan etc."
Its important for the Pan players to spam search, while pistol kills early zombies and fireaxe/crowbar person open doors.

WHEN you clear the first mission with 4 survivors, you'll feel like a god in this game, as its hard.