This is my current iron mine.Mining the surface deposits at night is risky. The screamers come quickly and their spawn can dig down or find the mine entrance easily. That said in V2 I am mining the surface nodes during the day, taking time away from trader quests.
At night I am tunnelling around really only for XP. That said. I have found Fe and K deposits, so only Coal and Pb day mining is necessary now.
My main reason for the post was to gain some validation that underground deposits in V2 are more rare than in V1 by design, not just some weird artifact of my random gen seed.

If any zombies show up, they tend to jump off the stairs, at which point I hear them hit and stab them before they get up. I've never really had an issue with screamers (they show up, but I almost always kill them before they scream. since they jump down before trying to scream.) Mostly, I just find them annoying, since they break up my mining rhythm/waste time on my consumables.