Are you playing on Nightmare?
Well...yes. But it's still insane and you would call me that if I didn't have a screenie as evidence.
To be fair, the number of spiders on this floor was only six or seven, which is doable compared to later on (when there are easily double that amount). It's not quite as bad as Caco vaults on the second floor (or first on AoP/A100/AoH) or Revs on the same non-cave floor. Hell, I ended up dying to a pack of Commandos (yes, a PACK, I didn't even know they spawned in packs) on the next floor instead.
I swear, as many times I've played this game, I still keep finding things that utterly confound me.