LFR. Wrathion. Zoned in and my character and everyone else is invisible and untargetable. Can see mine and everyone else’s shadow on the floor. I can hit the boss by using aoe spells, but it is untargetable. I can see the party’s spells (fireballs, ice spells, etc) hitting the invisible boss. The mini-map shows the location of party members. I fought the whole battle like this and it was a miracle I didn’t die, the healers and mini-map saved me. As soon as boss died, everything popped into view, including party and boss. The rest of the LFR went without issue.
This has happened twice now, but not every time.