Like in older versions of Divine RPG, still exists bug, when mob is invisible. You can hear it sounds, but cant see it. Can be fixed by rejoning server.

This is a forge bug, there's sadly nothing I can do about it.

But in other mods we can always see any mobs. Maybe we have any problem?

AoA has this same problem. IIRC, I first saw it reported for TConstruct. So, no.