I can sort of understand where you all are coming from. Skyrim difficulty is, to be honest, all over the place. Killing giants before level 15 is nigh impossible on Adept or higher difficulty, and mammoths I think are even stronger. I am playing on Expert difficulty, and have experienced quite a few deaths throughout. Sometimes, you just get bottlenecked by an enemy you're not quite ready for. That's what happens when a game doesn't level-scale its enemies. Point is, eventually when you gain hard-earned levels and build up your character further, you will come to realize that you are supposed to be a total bad-ass in-universe. Before long, basic enemies like regular Bandits and Draugr will be felled in a single hit, but encounters like dragons and powerful enemies will still maintain a good challenge. I prefer this method over Oblivion's leveled mobs, where eventually even roadside bandits show up in full on glass and daedric armor. With enough levels under your belt you'll still be quite easily top dog, but you just doesn't get the idea that your character's ... well, special anymore. Parading around in full ebony in Skyrim on the other hand is a mark of considerable baddassitude. When I finished smithing my ebony armor, weapon and shield, I went around touring the countryside all dressed up like the Black Knight, boisterously challenging giants and trolls and going all 'It's only a flesh wound!'.
Anyway, back on topic. Honestly, games like Oblivion and Skyrim are as hard as you would make them to be. It is really not a game where it is a sin to turn up or down the difficulty if it is too easy or too hard. Sometimes it may even be necessary to get out of a fight with an unconveniently timed dragon priest alive.
As for me, personally, my first and current character is a Nord melee fighter, with shield and axe. I use no magic; not even restoration, and depend for healing only on the potions I find in the game world. I use neither the offensive or defensive benefits that magic spells can bestow, because Nords take pride in their combat prowess. The only exception is Soul Trap which I use now and then to enchant gear and recharge magical weapons.
Difficulty in Skyrim depends a lot on gear as well. Much more in fact as that it did in Oblivion. Some items are incredibly powerful and influential, especially the unique ones. An example would be Spellbreaker, a unique Dwemer shield granted to you by the Daedra Prince Peryite. When blocking with it, it creates a magical field that 'blocks' a set amount of all magic that comes your way. High-tier fire mages and dragon priests that previously ripped me to pieces with massively powerful spells were suddenly a lot more manageable. Choosing the right skill perks can also cut difficulty in half, especially defensive skills, but these more useful perks are usually further down the tech tree of a particular skill.
That said, I don't remember mudcrabs in Oblivion ever being a challenge past, say, level 3. Now, Mirelurks in Fallout 3 on the other hand...