BTW, dtgreene, did you try Fell Seal? I don't remember if you said you liked tactical/sRPGs. It's relevant to this discussion because it has a fairly robust class system, some validating tropes, some deviating. (How about the aforementioned tabletop game, Gloomhaven? The whole game's character set is about bucking class norms.)
No, I haven't tried Fell Seal; I don't like TRPGs as much as I do RPGs with non-tactical combat. I might give it a try eventually, but I'll probably wait for some sort of sale. It's nice to see an indie RPG that's clearly inspired by Final Fantasy Tactics, but I would be more interested in one that took after the SaGa series. (Incidentally, in the one SaGa I've played that has classes, Romancing SaGa: Minstrel Song (PS2), I noticed that Hunter is a higher tier class than Ranger, which is not the way I would have done it.)
Anyway, here are how I would treat the classes (assuming a conventional distribution of roles; in other words, with clerics as healers and magicians as offensive spellcasters):
Paladin: A sacred warrior who plays like a fighter/cleric hybrid. This character would be able to fight well, and would also be a spellcaster (and spells would be a more prominent feature of this class than for the AD&D Paladin; this would be a true hybrid, not a fighter with minor cleric spells). Also, Paladin would be a title that needs to be earned; a character can't start out as one. (If running D&D 3.5, I would likely require all Paladins to use the Prestige Paladin variant from Unearthed Arcana.)
Ranger: A figher/druid hybrid. These characters would be able to fight pretty well, and would have access to druid spells, which would include a mixture of attack and healing spells (and, of course, some support and utility spells). This class would be the "jack of all trades" class, similar to the Red Mage from Final Fantasy (but balanced like the one in FF1 or FF3DS, not the rather terrible ones in FF3FC or FF5 (ignoring the final learnable ability)). Rangers might have some rogue abilities, further cementing their "jack of all trades" role.
Druid: A uses of nature magic. The druid's spell list would be unique, but would contain both healing and offensive magic, many with nature-related themes (like a thunder storm or a life water spell). They would not have the offensive power of a mage, and would not be quite as good as healing as a cleric, but would be able to both, and their offensive spells would still be stronger than that of a cleric.
Ninja: A bit of a rogue/samurai hybrid, I think. They would have abilities that do things like increase evasion, let the party escape a fight, assassinate an enemy (chance of instant death), and others. Ninjas might also learn a bit of ninjutsu magic, which includes medium strength offensive spells meant to fill niches that physical attacks wouldn't fill (like hitting multiple enemies, or damaging enemies that physical enemies wouldn't work on). (Incidentally, a rogue/mage hybrid might be another approach to this class, provided that rogues are decent offensively in the ruleset.)
Bard: Support characters. Their primary ability is the use of bard songs, which would provide the party with some benefit, such as increased attack power or health regen. They would not be meant as attackers (though they might get some offensive ability, just so that they have something to do when done singing or if alone), but would be rather meant for support. They would not get thief abilities; this means no ability to steal, for example. (I mention this because I find the AD&D 2e Bard, which is basically a thief/mage hybrid, to be rather unsatisfying.) Bards would not learn and magic aside from their bard songs, which could be treated as magic.
Samurai: Like a fighter, but sacrifices some raw fighting ability for physical techniques. Basically, these would be used like spells (and have similar costs), but would behave like physical attacks, possibly having effects like doing extra damage, hitting multiple enemies, being critical-or-miss attacks, or perhaps allowing the character to defend and attack at the same time.
Goof-off: Perhaps this could be a character whose sole abilities are to resist status effects, to survive otherwise fatal attacks, and to run away from combat. This class's abilities could be useful if combined with those of another; a character with both cleric and goof-off abilities might be able to survive when the rest of the party gets killed, and could then revive the fallen companions.
(See also Defilers vs Preservers in the D&D 2e setting, Dark Sun.)
One thought: It feels like it would be thematically appropriate for Preservers to get healing magic, but they don't. Perhaps Preservers should have been given the role that Cleric and (particularly in Dark Sun) Druids are given.
(There's also the whole philosophical notion as to why only the religious classes get healing magic in the first place. As an atheist, this dosen't quite sit right with me. I have been thinking of the idea of giving arcane casters healing magic, while divine casters would excel in destruction and mind-affecting spells.)