I have a friend, who shall remain anonymous, who told me that on his server, he ran Garuda, Ifrit, AND Titan Extreme with a guy who beat each of them by using the following exploit:

As a caster (BLM, I think, maybe SMN?), you can somehow "float" outside of the arena, making you invulnerable, so even if the rest of your party wipes, you can just DPS all day long and defeat the primal.

This has been done at LEAST three times according to my friend. Please look into it and stop this unfair behavior.