In general, I try to stick pretty close to the established lore. I think my biggest diversion from that path is probably how i role play my characters' combat knowledge and potential. It is my own personal belief that the class system should not be held as the bible for what your character is capable of, for example. I don't role play a gladiator or a pugilist, but instead, incorporate small tidbits of classes that make sense for my character to know. One, for example, is a former huntress from a Xaela tribe. She can thus use a bow quite well, as that was her primary means of felling prey. This translated directly to the battlefield once she came of age to begin participating in the wars that her tribe was involved in. She didn't know any "special skills" with a bow, she merely knew how to use it as a weapon. She picked up hand-to-hand combat over time because there were situations when the enemy would get close enough for her to require a means to defend herself. From there, she was taught how to channel aether through her limbs so that she might be able to actually HURT a Xaela male in h2h combat... Because, well, she's little, and they're not. So, she learned what could sort of be compared to the "fists of 'Element'" type monk skills, just a much more crude version. She later used that knowledge of aether control to learn arcanima in Eorzea, but found that she kind of sucked at it. She can only summon carbuncles, and they are pretty unruly and not at all helpful, other than being cute.
I like to think of the classes as an analog to real world skills, crafts and disciplines. An MMA fighter, for example, isn't usually just a student of Karate, Kickboxing, Taekwondo, Muay Thai, etc. They learn bits and pieces of all of these different fighting styles in order to be competitive in a fight. You do have boxers who only box, so these would be your people who are dedicated only to one class, but then you have the veterans of war and sport that realize that they need a more diverse platform to ensure they remain victorious in their feats. Personally, my taste in combat tends to lean more towards realism. I don't like it when Lalafells beat up Roegadyns in fist fights. Sure, that Lalafell could probably roast the Roegadyn's ass if he used magic, but fisticuffs? Gorillas can physically snap a human's neck with a single blow. Roegadyns are bigger masses of muscle than they are. I don't think you'll survive! For someone to beat a physically superior foe, I tend to feel they need some sort of explanation. If a Hyur squares off with a Roegadyn and the hyur wins, I'd expect that the Roegadyn is either extremely drunk, not a trained combatant (whereas the hyur is), or the Hyur manipulated aether in some way that gave him an edge the Roegadyn did not possess. However, the story has a couple instances of lalafells easily besting other trained fighters like it was nothing. Especially in 1.0.
I like to think of the classes as an analog to real world skills, crafts and disciplines. An MMA fighter, for example, isn't usually just a student of Karate, Kickboxing, Taekwondo, Muay Thai, etc. They learn bits and pieces of all of these different fighting styles in order to be competitive in a fight. You do have boxers who only box, so these would be your people who are dedicated only to one class, but then you have the veterans of war and sport that realize that they need a more diverse platform to ensure they remain victorious in their feats. Personally, my taste in combat tends to lean more towards realism. I don't like it when Lalafells beat up Roegadyns in fist fights. Sure, that Lalafell could probably roast the Roegadyn's ass if he used magic, but fisticuffs? Gorillas can physically snap a human's neck with a single blow. Roegadyns are bigger masses of muscle than they are. I don't think you'll survive! For someone to beat a physically superior foe, I tend to feel they need some sort of explanation. If a Hyur squares off with a Roegadyn and the hyur wins, I'd expect that the Roegadyn is either extremely drunk, not a trained combatant (whereas the hyur is), or the Hyur manipulated aether in some way that gave him an edge the Roegadyn did not possess. However, the story has a couple instances of lalafells easily besting other trained fighters like it was nothing. Especially in 1.0.