How come physical dmg is sometimes greatly reduced?

I saw it happened to my friend just a moment ago, and it brought it back to my attention. Sometimes, with melee attacks, when you attack it makes a sound almost like a block, and you deal less than half of your normal damage. The enemy doesn't block, though (or at least it doesn't say it.) Why is this? And does Dex affect it any?

Well I've never observed it with a bow; my friend was using an axe, and when it happened to me I was using a spear. It's almost as if the weapon just bounces off the enemy, instead of penetrating it or whatever.

It's never a block, and it's obviously not a miss...but it just happens sometimes and I hate it lol. It's happened to me more times than I've noticed it with others, though. My regular attack with Omega Strike is around 1.5k, but then when this "event" occurs, I'll do around 600...I just don't know why it does this.

I just thought the hit was blocked a little, but maybe thats not it

sometimes triple nock or any attack that have 2 or more hits

miss 1 hit or 2 or even more depends on number of hits the skill has

so the dmg get lowered

and for blocks in 1.00 block lowers dmg by 20%

but in 1.01 block lowers dmg by 40%