In FF games, its always has been " Having the the right combination of Class/job" Always need a couple healers, or else your Tank/party will die, Always need a Tank or your party won't last against his/her attacks, Always Need DD/nukes to take down your foe, if you have no Damage you won't kill the foe ( especially a boss).

You do need " somewhat" of a setup. The DD aspect of it all I get anything related to Damage. BUT, I always get a GLA/2~3 healers/ Rest DDs. If you don't have that Basic Formula, You will die @ a boss at the very least.