Ironically, Pokemon games have a hell of a lot more depth than this game does when you get into the competitive scene, it's one of the examples I'd happily give as "easy to learn, hard to master".
If it adheres to FF5s job system, can I put Black Magic on my White Mage? How about give my WHM a greatsword? This game does the opposite of FF5s job system in that it's very static, the job is the job and you don't have much say in how it develops, whereas 5 lets you experiment with different passives, bring in new spells/abilities from other jobs, etc.
FF1 WHM still could wield hammers, making them good for picking off enemies early game, later it would get Dia for undead enemies and Holy for anything else. It was primarily a healer sure, but it still had offensive capabilities. FF3 gave them Aero and debuffs like Silence. Rosa could wield bows and Porom could Twincast with Palom. FF5 as mentioned earlier you could give them another jobs moveset. Garnet, Eiko, and Yuna were also Summoners. All WHM had some offensive capabilities, and the ones that don't had supporting systems to give them offensive capabilities anyway. The closest to "pure healer" you get is FF1.
SCH has been around since FF3, FF11 as well, and was known for being a user of both Black and White magic. The fact that a legacy job like SCH is now relegated to being a WHM clone (but with shields) already tells me Square doesn't care for tradition and is willing to sideline it for the excuse they call healer design in this game.