You can easily dispatch a wolfpack late in the game - but what about a pack of WHATTHEHELLISTHATMONSTRUOSITY?
For the most of examples I used a very simple but effective system we had in Gothic. It was surely not a wasted time. Being hunted by monsters was the first time in an RPG I really feared a mob.
I hope there will be a lot more variety of weaponry than just swords
But I think I explained the issue of picking right weapon for the right opponent in the "Melee" thread.
I totally totally agree with you. There aren't enough games that have the courage to hunt the player down with monsters and ambushes after ambushes. Having some super strong monsters that encourages player to use strategy rather than button mashing and potion chugging would be great. One problem Skryim has is that all monsters are fought with the same strategy, mash your attack button, then heal up when you are hurt. If the monster is too strong then the only way to kill it is exploiting it. That's just bad game design. If I'm in charge of designing monsters in Skyrim, I would give troll a strong charge attack that stuns itself after use and leaves the troll open to attacks rather than give it a lot of attack power and unkitable thus force players to jump on a bit of rock and shoot the troll to death with arrows. Another problem I have with skyrim is just how awful the loot system works. Giants only drops their toes, trolls drop troll fat. These are utterly useless for many play styles and can't be sold for much. It does not provide an incentive to raise up to the challenge and kill those totally unbalanced and boring monsters.
Picking right weapon for the right opponent is a cool idea but it should not be over done. Arbitrarily making turtles totally immune to slashes would only be annoying. Sure smash turtles with a big hammer would do a lot of damage and crush the little thing's bones. Swords should still be somewhat effective against armored targets.
My suggestion would be giving weapons different fighting styles that the player can switch from one to another, like the fast, strong, group style in Witcher. even though it is poorly implemented in that game, it's still a good idea non the less. Since all attacks are going to be made by pressing the left mouse button in certain ways, it would be a waste to not give player the ability to switch between different fighting style.
Such as a fast style that has very little attack lag so you can immediately parry after one strike, a power style gives powerful slashes but put you off your balance if the attack did not connect, a charging style grants you extra range and can be used against far away monsters and armored foes.
As an example, if you are using a katana, the fast style would be a more agile moveset, in which you are focused on attacking the foe's weaknesses (neck, unarmored parts) and retract your blade more than using brutal force.
The power style would unleash slashes that are powerful enough to sever bones, however because you are using your whole body to swing your blade, it is harder to recover from it.
The charging style would either be a powerful running thrust to pierce armor, and a dashing quickdraw that will reach your enemy's neck before he lift his sword.
This not only encourage players to learn about monsters, but also make the combat all that more interesting. Switching weapons around sounds good on paper however, in most games with rpg elements, the player will only have one good weapon that he uses a lot. It is realistic for hunters to have some backup weapons and traps, but for a rpg game whose sole goal is to get better drop, it is simply not possible.
It's just my 2 cents though. May be people would prefer to button mash their way through the game, I can't speak for them.