Forgive me, I'm not trying to be condescending here. Merely trying to present an argument and a personal opinion.
When it comes to Final Fantasy games, and their leveling/combat systems, its fair to note that the games generally grant a wide degree of flexibility. In FF12 and FF13 (and FF10, and FF7 and FF8) you can basically tweak the characters to be anything and everything with enough grinding.
Based on my experiences, I've never had to grind in FF12. FF12's License Board itself is fairly open ended as well compared to the structured leveling of the Crystogen, or the Sphere Grid. Since modern MMOs (and FF14) are defined heavily by roles and abilities, I see FF13 as more of MMO type game with things like Tanks such as the Sentinel Paradigm. Whereas FF12's (non-international version) license board did not really construct itself toward a specific role. You could pick your weapons and have a somewhat unique experience with it between others, but ultimately it didn't vary much. There's no prescribed tanking class, damage-focused class, or healing class. Every character could pretty much pick up everything with fewer limits that what's in FF13 or FF10.
I don't really see the License Board or the Crystogen system as anything like an MMO skill tree. Usually with those, you're presented with choices and limit on the number of choices you can make. In either case, FF12 and FF13 don't really have hard limits on choices you make, or the choices are an illusion and you're merely filling in points (ala Sphere Grid). In either case, neither of these systems really constitute a traditional MMO skill engine. Nor was I arguing that FF13 was trying to be like an MMO. All I said was that FF13's combat system is on the shallow side as it takes elements of MMO's combat structure and roles to a certain extreme (Tank, Healing, Damage, Buff, Debuff). Not that the game was being like an MMO (because it isn't).
Any who, that's just my opinion. I've hoped clarified my points a bit better.