Isn't this fine? They should be easier to fight with +3 weapons. That should be the benefit of owning a +3 weapon.
I don't consider it fine or "unfine". It is expected. And in 4E, if you play a 16th level Fighter with a +1 sword, an equal level Giant will be harder to fight than if he had a +4 sword (as would be about expected). So no real difference, right?
Except that the game tells you that a 16th level character with a 16th level gear can expect a similar challenge to deal with a 16th level enemy than he did as a 5th level fighter with 5th level gear against a 5th level enemy. Isn't
that nice?
I'm not sure I understand the point you're making here. Are you essentially saying that it's easier to gauge challenges if you reduce party power and monster challenge to a single number? In that case, I agree, but I don't understand where the Fighter/Wizard reference arises in this context. One thing, though, where I think I disagree with you; I don't think that that single number should be used as a complete straightjacket - I think it's more interesting if the game has a variety of monsters, some more easily defeated by some classes than others, or by some methods than others. The "simple number" (in my opinion) should be a general guideline, not a hard-and-fast rule. Eyeballing the challenge should always be helpful.
You can always add variation in multiple forms. Monsters don'T have all attacks, damage and defense values identical. They have weaknesses and strength. It is a baseline for that level. In addition, you can vary the level of the challenge by using monsters of different levels.
But you have this nice baseline: "A nth level player character with nth level gear will find a nth level monster a reasonable challenge".
I don't think this is true - you can instead end up with "Average the party level; add +1 if they mostly have +2 or +3 weapons and +2 if they mostly have +4 or +5 weapons. This is the party challenge strength. Match with appropriate monsters, such as the Level 5 Mini-giant."
So the bonus items aren't "baked into" the math, there's no assumption that a party must have them to make the challenge ratings work; instead there's simply an accommodation made for them in the calculation.
That, I think, could also be nice. If the "average gear level" or "plus level" of the party could be applied as a modifier to their level.
But again, on a fundamental level, I disagree with even having +x items at all. They only change some math things. They don't create a different style or thematic element. And from a pure gameplay point of view I still maintain that the "difficulty" of an encounter or scene will always have to fall into a certain range, so if you give your players +4 weapons, you will want them to challenge with a little harder foes, otherwise they game will become boring.
And then there's the idea - maybe you don't even want to have every character use a magic weapon just because he fights with weapons? What if one character has a heirloom sword - non-magical, but with great meaning? You give the other character a +4 Greataxe, and he's happy hacking away at enemies with it, while the "roleplayer" that wanted to keep the ancient sword his grandfather already wore into battle.
Also - when you have +x items, you naturally will want enemies where you "need" such items to hit reasonably often. But this in turn basically requires you to have enemies that you will auto-hit and auto-miss at some point. We only use the d20, so you have to accomdante another +5 modifer to defenses for magical enhancement, when you also have to take into account all the other bonuses that players get. You easily go far beyond the d20 range with the possible values people can reach. But is that really desirable?
So I think the +x items only add complexity to the game, but doesn't really add to story and enjoyment of the game. It just causes another risk to it, and more boring math(which is also a risk to enjoyment for plenty of players), and mathematical artifacts.
Focus on the story and flavor of the magical items, and you gain so much more. You can have a Fighter being known for his mastery of fire thanks to his Flaming Greataxe, instead of having a Fighte whose only shstick is that his stick has a higher abstract number than another stick.
And you can have him alongside the Fighter with his heirloom. He is renown for his martial prowess and cunning, and still wielding the sword of his ancestors. But the players don't have to mind, their characters are still equally effective, they look and feel very different on the battlefield, but they both still can defeat their enemies equally well.
