Pretty sure darkness is either a set % to miss, regardless of your accuracy, or it has a minimum % that you miss regardless of your accuracy. My level 200 corsair friend still misses under darkness and he has close to 1,000 accuracy. I don't notice him missing less than others, either.
If you miss on Iron Mutaes in 3x, try Sniper Pills from Ludi. If you still miss, 100% a bathrobe for DEX until you reach 35 and can 100% a warrior overall. Or, go and do the Mushroom Castle quests. Those will get you to 35 easily.