I encountered this bug too today.
It appeared often after I used "teleport" and monsters were close to me. So it seems that my spells (Annihilation for example) couldn't hit them because they stand to close to my.
I hope they can fix it soon.

i only encouterd that with wrath of baapeth, wich is following discord not a 360 degrees damage skill

I have this issue all the time - very noticeable with Wrath of Baapeth too. @Shizukana08 it doesn't feel like it's a hit box issue / area of effect issue

Can't complete the western tower because of this. On several attempts, the first wave on the top can easily be killed, after the cut scene the "boss" bugs out and no longer takes any damage. It's as if it lags out. The best fucking thing about this, is that I was going for the act3 no death achievement now I have no idea if I fucking died or if I can pass the fucking level.

EDIT: still fucked after the 1.0.4 update

I encountered this bug of the skill Flight of Gavanaar not registering damage. I didn't notice this prior to this patch. Now with this patch 1.0,5 and 1.0.6.0 I instantly notice this is a problem for me. Please FIX!

I got this bug too and its like 80% of my dmg is gone and after the last patch this bug is more often as before