In third person, it would be hard to do complex combat without auto-target, detailed navigation using wasd in 3rd person is tricky. What I'm getting at is that combat can be very simple and challenging at the same time, block when needed strike back vurnable foe's. For example WoW has this system, quite the best system I've played with in 3rd person (mmo)RPG's, one difference with what Lepel and I are getting at is that combat/spells will rather be performed by simple key-combinations (shift+ hold mouse1 = inferno) (run + mouse1 = beserk) (run + mouse 2 = shieldbash), and not the usual 1234567890 or F1 F2 F3... keys.
Personally I find it easier to use simple combo's than using the Function or numeric keys.
In 1st person, auto-target would be lame, and combat would involve many mouse/wrist movements.
Try Rakion (from softnyx, its free but you can buy benefits if you want) if you have the time. (and feel like it)
It isn't a RPG but it has a somewhat more complex fighting system (without auto-target) in third person. So if you swing a sword or another weapon and it misses its your own fault.
But this game is all about timing and learning about the enemys attacks (and the delay time of their attacks). It might not be an ideal fighting system for a single player game. So don't think I would want a fighting system like that in the game. But I'd prefer it over the gothic 3 or oblivion fighting system.
I find it easier to use simple combos too, thats why I wanted them to be customizable since I know this is different for everyone.
And imo 1st person would be lame, auto-target or not. (but the third person view available in oblivion was even lamer as its 1st person view)