SCH wound up mish-mashing Geomancer and Sage, really. Not exactly the end of the world unless someone out there was really craving an axe-wielding nuker (Though I guess that'd make Farsha more appealing?). Actual Geomancer mechanics would be a nightmare in FFXI as they'd then have to go through and map all standing areas with location mechanic, and frankly, how often are you going to find water-based mobs in a lightning-friendly environment?

Far as RDM goes in its multiple iterations, it's 1 part Warrior, 1 part White Mage, 1 part Black Mage. Anything built on that is gravy like enhancing and enfeebling (You know, SE starting to be imaginative 'n all...). Take away the melee and you get Sage or XI's SCH. Take away the Black Mage and you get Paladin. Take away the White Mage and you get Dark Knight. It's a job meant to work hand-in-hand with all of those parts. I used the baseball analogy because its core concept of a ball being pitched to a batter who tries to hit it and thus round the bases without striking/tagged out is what makes it baseball. It then proceeds to vary in the speed and type of pitching, distance between bases, and how big the field is. When you start changing stuff to be more broad like "guy with a stick hits something" then you start stepping into hockey, polo, tennis, lacrosse, and whatever variant most definitely not baseball.

Unfortunately, FFXI hasn't been very friendly toward RDM's hybrid needs, and applying that word doesn't mean it can't carry its own specialty in the process. And to imply it can't be done is again folly and demonstrative of your own lacking imagination.