That isn't true. the Terminology is older then MMO's. so is the "Trinity" though in FF's its never been a true trinity. Its always a Mix of 6 roles.
Tank, DD, Status, Healer, Elemental, Suberter.
Which Magically is exactly what the first 6 jobs are as well.
War, Monk, Red Mage, White Mage, Black Mage, Thief.
Just depending on how many character slots you mixed them up and sometimes fit two of those 6 on one character.
Tank/DD, Healer/Status, Subverter/Elemental, Elemental/Status
Also Just about Every Final Fantasy not all but most, Have this ability called Cover. Its a neat ability. It makes one character jump in front of another and defend it. Much like a Tank would.