I have mixed opinions, it seems like a mess of the leveling system yet again, they seem to be trying to find a middle ground between everything becoming too easy like in Morrowind, and the level scaling mess from Oblivion, by using a combination of level scaling and planned encounters.
I do tend to agree that some enemies are FAR tougher than they should be, Cave Bears, Ice Trolls, and some of the human enemies like mages and Forsaken leaders. I also suspect some of these might be bugged though, for example I notice a tendency for enemy mages, especially dedicated wizards, to never run out of mana, and this includes when they are getting hit by some very high powered mana drain effects. On top of that it seems that NPC hit points scale in a way that doesn't match player progression, an enemy mage is liable to have far more hit points than your mage because the program doesn't make allowances for mages being fragile. Basically the NPCs aren't developed under the consideration that your choosing Health, Stamina, OR Magicka every time you level.
Of course a lot depends on your build as well, some builds are far more optimized than others given the way perks work. I think that like other games in the series there is a definate focus on melee, where it seems it's much easier to build a powerhouse of durability and damage dealing that way than it is with magic (not that it can't be done). I've experimented a bit with magic and melee and an optimized warrior is going to be dishing out more pain than a dedicated mage on average given when he's liable to be carrying for weapons.
That said, I think Bethesda is on the right track here, I think it's more statisfying than either Morrowind or Oblivion. Really my concern is that rather than trying to balance the game they are going to continue to remove options to leave only very simplistic, optimized paths, and less options to reduce the chances of making a gimpy character rather than finding ways to ensure there is no such thing as a gimpy character even with all those options.
Of course then again I do tend to notice that the number of skills goes down with each installment.... and in this one the magic system took a major blow, given that there is no spellmaker that I can see, and very few spells over all.
I will say though that this game is balanced with the assumption your going to be bringing NPCs with you, despite the AI issues. As you level up I think they consider the odds of you going it alone are considerably less. Seriously, things get a lot easier with an NPC along, and also being able to summon stuff helps a lot. Even if your not a mage getting Sanguine's Rose is fairly easy (and you can constantly recharge it with soul gems). So you should be able to have an NPC and a level appropriate Daedra with you in any tough fight after level 14. Also, don't just focus on your character skills, remember the shouts are there for a reason, some of them are kind of useless, but you can do things like freeze an entire room of enemies which paralyzes them and puts them under a DOT until they break free (as long as you don't attack them).
Just some points to consider on the end there. If your not using everything availible to you, some of the battles, especially the big rooms towards the end of dungeons are going to be rough.
That said, there is no way a mage should be able to survive getting the Mace Of Molag Bal bounced off his head 10 times, and he sure as heck shouldn't have any mana left. I think the issue is that the hit points are based around dedicated melee builds, and need to be lowered in some places for targets that shouldn't be quite that durable.... I can't even begin to express the unreality of running into a Cave Bear that seems to be more durable than a Dragon.... yes bears are tough, but they are NOT sherman tanks.