I'm talking more about player psychology than statistics.
I think the difference in our approaches is that I'm coming from a purely mathematical angle.
Its not the variation of the numbers that is the problem, the problem is how visible the effects of that variation are.
However, from the mathematical perspective, the variation is the problem.
My comment wasn't pertaining to the tactical details of combat, but to monster design space. In 4e the monster defenses are determined by a formula similar to this:
Defense = 10 + (monster type bonus) + (1/2 Level) + (Level/5 rounded up to a whole number)
A PCs attack bonus is determined by a formula similar to this one:
Attack bonus = 10.5(aka d20) + (weapon proficiency bonus) + (1/2 Level) + (Level/5 rounded up to the nearest whole number)
4E's monster math for defenses actually works out to:
Defense = 10 + (monster type modifier) + Level
This discrepancy in the formulae is why some players believe that the Expertise feats are "taxes" and that without them, the players' attack bonuses fall behind monster defenses by too much as the PCs gain levels for them to enjoy playing the game.
If you plot these two formulas on a graph you end up with a pair of narrow bands that stay parallel even when they jump after every 5th level.
The graph itself is a representation of the available design space, and the band are how much of that design space is taken up by 4e. If you remove the "(Level/5 rounded up to the nearest whole number)" portion of the formulas and then plot them again you will find that the band take up the exact same amounts of design space meaning that the (Level/5 rounded up to the nearest whole number) portion is meaningless from a design space use perspective.
I don't like when something is meaningless when it could actually be used to expand how design space is used.
Removing the attack bonus from magic weapons from both formulae doesn't actually expand the design space. Don't mistake the consequence for the cause. If you want the PCs to have a certain chance of victory over the monsters, and you want fights to last a certain number of rounds on average, you need to have a certain relationship between monster defenses and PC attack bonuses, and monster durability and PC damage output. Given the simplicity of the monster defence formula, I suspect that it is the base formula, and the PC attack bonus formula was put together based on traditional sources of PC bonuses: ability scores, level, magic items and feats.
Like I mentioned, there is some scope for trade-offs - lower defences can be offset by higher durability, for example, but the trade-offs are quadratic (or possibly asymptotic), not linear, and the difference between trade-offs at extreme ends of the "to hit" probability scale can be quite substantial. When you hit 50% of the time, a +1 bonus to hit increases your damage output by 10%. At this to hit chance, reducing monster defences by 1 point can be offset by a 10% increase in durability. However, when you hit only 5% of the time, a +1 bonus to hit increases your damage output by 100% (ignore the effect of critical hits for now). At this to hit chance, monster durability needs to double to compensate for a 1 point reduction in monster defenses.
Math will not expand your design space. Willingness to accept more varied outcomes will. Math will tell you what are the likely consequences of tinkering with the default elements, though. If you are willing to accept that some fights will take half as long (or twice as long) math will tell you that you can halve (or double) monster durability, or you can adjust monster defenses so that the PCs hit twice as often or half as often.
So your answer for having to much design space is to get rid of the excess?
Nope, the answer is to reduce the variation in bonuses from magic items so that what weapon you are using matters less to your hit chance.
You can call a rabbit a shmerp, but that doesn't make it any less of a rabbit.
Exactly. The math doesn't care where you get the bonus from, as long as you have the bonus. If you want more freedom to vary the PCs' equipment while maintaining the same battle outcomes, just make sure that the bonus that the PCs should have got from equipment comes from another source.
All they are doing is hiding the symptoms of the problem and not actually solving the problem.
They solve a problem. Admittedly, it might not be the problem you have in mind.
The level 17 character still has a better than even chance to win.
Sure, but the question is: how significant is his advantage? Most people would be hard pressed to tell the difference between a fair coin and a coin with a 55% chance of turning up heads until after they have flipped both coins several times. Most games also tend to feature monster vs. player battles more than player vs. player, and the PCs would also tend to be similarly equipped. A player with a 15th level PC and a +3 magic weapon fighting a 15th level monster would usually only know whether or not he defeated the monster, and not whether he would have done better with a 17th level PC and a +1 magic weapon.