Is it just me, or is 4E particularly prone to over-scaling? The semi-mythical page 42 seems to exemplify this.
4E is prone to over-scaling in much the same way that a bicycle with training wheels is prone to being over-balanced. If you want don't want the training wheels (because removing them improves the biking experience for you) you'll have to take them off yourself. If you want greater variation in the PCs' chance of successes when it comes to hitting monsters and making skill checks, vary the levels of the monsters and the challenges they encounter more.
As for the oft-maligned +X magic weapons,
Dice4Hire pretty much nailed the issue. If magic weapons are going to provide a widely-varying bonus to hit (say, from +0 to +5 or +6), then "the math" is going to have to take this variation into account. As far as I can see, there are a few ways to deal with this:
1. Significantly narrow the band of potential attack bonuses from magic weapons. Maybe a generic magic weapon gives a +1, and an artifact-level magic item gives a +2.
2. The inherent bonus method of building the assumed increase to attack bonuses from magic weapons into the game's math, then providing an alternate approach that would attribute the required bonuses to the character without using magic items.
These two approaches effectively sidestep the issue by minimizing the magic weapon's effect on the PC's chance of hitting a monster.
A third approach works by addressing monster selection, in a way similar to the "+X to hit" rules of earlier editions. Suppose monsters had a value that indicated their level of magical protection, ranging from +0 (for normal monsters such as humanoids and giants) to +5 or +6 (for highly magical creatures such as high-level devils and demons). This bonus would be factored into their AC and other defences.
Then, when a DM is picking monsters for a game, he can ignore monsters with a protection level higher than the magic weapons that the PCs have. If the PCs only have +1 magic weapons, for example, he can ignore monsters that have a +2 or higher protection level.
Actually, come to think of it, he could use monsters with a +2 or higher protection level, but he would have to use lower-level ones. Assuming a scaling system similar to 4E, a party that can take on a 10th-level +1 monster should also be able to take on a 9th level +2 monster (since their defenses would be approximately the same).
In fact, you can probably generalize it further, by giving monsters an Effective Level (MEL) equal to their actual level plus their magic defense level, and smilarly giving PCs an Effective Level (PCEL) equal to their actual level plus the attack bonus from their magic weapons.
Even better, by working backwards, you can even apply this right now to 4E: Divide the PC's level by 5 (round down), and reduce his effective level for every point that the bonus for his magic weapon is below this number. Lower the levels of the monsters he encounters accordingly. So, a 16th level PC that only has a +1 magic weapon should be treated like a 14th level PC for the purpose of which monsters are considered suitable challenges.
I think it just might work.