Party chat is useful for reporting the number of fates in an instance and directing the party if you are farming FATEs, be they in a new expansion or in Eureka/Bozja. It's not practical to use during combat like in FF11 because of how high APM FF14 is, with the player having to be constantly pressing buttons to deal damage and evading AoEs. No time to talk like in FF11 where you press an ability once every 10 to 30 seconds.