Ok. So far this has happened to me on at least four separate occasions. The first time being in Stone Vigil, the boss: Isengrad. Everything was just peachy for that whole Stone Vigil run until I got to the last boss, which I could not see. I could target it, I could attack it, but I could not see it. Now, I was able to complete the encounter with relative ease, but it continued to bother me. Now, I have witnessed this same phenomena with the Halatali Hydra as well as Ifrit (Hard Mode). I just did the Hydra today and both times I entered the duty, the hydra was invisible to me only. The others in my party could see the hydra clearly, but I could not. This time it turned into a detriment and I died several times during the encounter. The same thing has happened the last two times I've done Bowl of Embers (Hard). Ifrit is invisible the entire fight. Even his clones are invisible when he charges across the map. This has caused me a lot of unnecessary difficulty in clearing these encounters. It would be awesome if something could be done to resolve this issue!