Quote:To clarify: your Def is set to zero when running, so melee monsters will always hit you if you run past them. (Unless you have a method of blocking; see below.) Walking does not affect your Def, so if you are playing a character which relies on Def, you're better off walking near monster packs than running.
To clarify more: it's not that your defense is set to zero. It's that the chance to hit roll is an instant 100%. That means you lose your defense and your level advantage and it's not capped at 95%. So a quill rat in act 1 normal would have a 100% chance to hit a running clvl 99 iron barb.