Let's see... First, combat melee or not needs to be more dynamic, fluid, and reactionary. For instance, if my character slashed somebody from across the face with a right to left blow, I'd expect to see a trail of blood along the path of the blade, as well as having the enemy's head move to their right a little, and the same to happen if my character was hit in the same way. If I strike their armor I expect to see some sparks during the strike and some scorch marks left on the armor afterwards. Arkham Asylum/City did it, proving it's possible, so now the Elder Scrolls can do it. The strikes for both combatants should be based on what the other is doing, i.e. aiming for the lower body if their opponent is blocking their top half or something like that.
Second, since everybody here seems to be ragging on QTEs, (I LIKE QTEs for the record) how about as a compromise something based around timing? For instance, like the OP suggested if you tried to sneak up and slice a too strong enemy's throat, you'd enter a struggle with your opponent. What you'd have to do is push the strike button at the right time (with an optional on screen prompt as to when to help the player, nothing intrusive or immersion breaking, like a split second red flash or something) to gain ground on the struggle, and if you failed too many times the enemy would hit you, cause some damage and proper combat would then begin, but if you succeeded enough times you'd instakill the enemy. The more skilled you are at sneaking and the weapon you're using, the greater the margin of error you'd have.
Something similar to the above for blocking. Say, you're surrounded by 4 opponents on all sides, who all attack you pretty much at once. If you press the block button about 4 times each at the right time, you block all damage from all of the attacks in a fancy manner with your weapons and/or shield and stagger each opponent, (say, block one strike with the shield, another with the sword and then dodge the other 2, or if you just have a sword block one after another) and then if you press the strike button with timing to counter attack on one or more of your opponents in a similarly flashy fashion (say, bash the guy in front of you with your shield while you turn your blade around and stab the guy behind you in the stomach for example, they'd be dependent on your weapons or lack thereof). As above, the higher your block and current weapon skill the more time you have to react between presses, maybe even throwing in some slow motion, but in either case you wouldn't have more than 2 or 3 seconds to react even at max, to keep it from being OPed. Throw in something like that for dodging to finish the whole thing off.
Of course, similar timing would also be required to prevent your opponents from blocking and counting YOU.
