How is the Sling starting item meant to be used?
A player taking it can only take another starting item that make them move 1 if they are lucky (or 2 on a 4 with the axe) and as nearly all enemies want to make their attack from the same square or adjacent after the first round the player is likely to always have people on top of them or adjacent meaning the range 2 to 3 sling basically becomes useless for most of the fight.
Just chiming in here, as I also think the sling could use some sort of tweaking. I picked it and the longsword as my starting build along with the striding boots. I played through the Grim Coast realm and I don't think I ever used the sling unless I literally had nothing else to do. There was just never a situation where using it would have been strategically better than using the longsword.
I got my ass handed to me so many times during that realm (I think the rune lord took me like 6-7 attempts). I first chalked it up to me being new to the game and not fully grasping the rules at that time, which was certainly true to an extent. But when I moved on to the next realm, this time using a longsword and shield, I found that I was doing WAY better in combat!
Perhaps that simply speaks to the necessity of having a shield, or at least some sort of weapon that provides Block, rather than the sling's weakness though.