I've got a full set of shadow armor and a full set of meteor armor but everytime I try to mine hellstone, four or five of those freaking fireball rats spawn and kill me after like six seconds. I know my pickaxe can repel the firebalss, but they spawn on both sides. What do they expect me to be able to do..?

Use potions... also, dig down in a hole two blocks wide, they wont spawn down there with you as long as you fill the hole left from anything you mine.

I too feel your pain. Hellstone is really hard to get when you're constantly getting mobbed by 4 fire imps and 3 skeletal worms... I can't kill them faster than their spawn rate!

The best strat is to ignore them and mine as quickly as possible. Bring 30 potions and a friend if you're playing online.

Patched to version 1.05. Now it's relatively quiet in the underworld.