I thought someone already reported it but i couldn't find a post about it so:
In T4 fracs and CMs (not sure if anywhere else) to me and my group happens daily, that we are quite literally missing enemies. Only thing that is shown is their hitbox that we have to target with tab button usually. We cannot se their animations or anything. Happened multiple times on Arkk for example but it happened a lot on other bosses like Skorvald or MAMA. Also in Twilight Oasis at last boss some people from my group either couldn't see her at all, or animation showed that she just stood there without doing anything but attacks were still happening.
I got gw2 on SSD and it happened to me few times as well but i guess not as many times as to other members of my group.
Please fix this ASAP because its super annoying, makes me want to quit fractals when this happens.