"Wing Tsun" immediately came to mind, but oh! 'tis about RPG after all
Well. There's either the real-time action style where you only control one character, as in Gothic or the aforementioned Diablo for example.
Then there's the party-based system that comes either in turn-based - like FF - or in pausable real-time as in Baldur's gate.
As I see it it the first decision that should be made is whether or not you want to create a party-based game.
The latter usually offer a great deal more in terms of strategic possibilities when it comes to positioning characters on the battlefield with different strengths and weaknesses to get the most out of them.
Pure real-time is less strategic as you only position yourself towards enemies in a way as to not be caught up between them or remove some of them from the battle temporarily via crowd control, the strategy is mostly confined to that and building and outfitting your character between battles.
Having said that , the best experience I had personally was playing the real-time Dungeons and Dragons Online as a single character as part of a group of other human players, mostly as battle-bard, coordinating my teammate's actions via voice chat, providing crowd control, healing friendlies and singling out enemies in melee combat. You have very good flow of battle, have to think and act quickly and diverse characters provide a wide variety in strategic options. So the more strategic options in forced real-time combat, the merrier for me. I like to be forced to make quick, game-changing decisions now and then.
Real-time will require a lot of work in movement patterns, attack styles/speeds/ranges I guess, more like a shooter. Turn based sound to me like a game of attributes and decisions.
Don't know if all that makes sense