Dps jobs are easier to diversify compared to tanks and healers.
not anymore really. they made smn too much of a dot person and less of someone who uses their pet to do damage. if they had made summoners more pet oriented then i could see rdm come in and be a dot dmg dealer. atm i can't really think of something any new job would bring. mch was just a different brd and
But it's still diverse in being the only job like that so far.
You're looking it more as SMN not being a pet job, and that's mostly a fault on SE's part because they've made a game where it's hard to pet jobs to thrive without making the pet be basically totally useless.
I'd love to see them add actual pet jobs to the game, but as the combat system is now it just doesn't seem like a possibility without them ending up exactly like SMN and MCH.
drk was just pseudo-war with different abilities.
DRK is far closer to PLD than WAR, and this possible idea for SAM seems more like their "WAR Alternate" if it turns out to have any actual basis in fact.
The problem with trying to diversify Healers/Tanks is that like you said, this game is very scripted and thus tanking and healing is going to be incredibly similar no matter what name you put on the job doing it because they need to have extremely similar abilities to handle mechanics for that role. Thus we get the problem where DRK and PLD feel like nearly the exact same class with different ability names.
Healers have the same issues, where AST is still trying to properly come into its own because all anyone wants to do is compare it to SCH or WHM rather than being its own being with different situational uses.
DPS can almost always be diversified though because as long as they can deal large amounts of damage they're doing their job. They're not required to do much else.