Purify didn't stop CC. Back then remember PLD had their full PvE kit, which meant they could stun you three times, silence you, and white mages could bind and knockback you. You had the one purify, to deal with ten seconds of CC or more. While you could deal with it, it really made matches unfun, and if you weren't good as a healer (not just average, very good) you were a liability and got reamed out. This actually over time led to the chat ban.

And honestly, they should think about balancing for feast and frontlines separately. two or more healers in a frontlines mode can soak up damage to a ridiculous degree. It's killing rival wings imo.