It's much easier to simply level up a character, get lots of equipment/items, or create a powerful spell than to master a combat system.
That really depends on the combat system. 99% of the time, the opposite is true. It usually takes a lot more time to level up your character than to master the ins and outs of a combat system.
For us gamers who are good at action games, we'll master the combat system very quickly (usually takes me about an hour), and then any sense of progress - of getting stronger - goes away.
This also assumes a deep combat system, and let's be realistic, that's not going to happen. Combat will be improved from Oblivion, but if you're expecting a Ninja Gaiden learning curve, I just think that's totally unreaslistic.
***Again, I don't want to make it sound like player skill is unimportant. It *IS* important. It's just that stats should be king, with player skill coming second.