For any Wizard (that doesn't use Golden runes and/or the passive that makes academic/signature skills add arcane power) the only regeneration you have is passive. Of two weapons with equal DPS, but one with a slower attack speed, you overall better damage for the skills that actually spend arcane power, while your academic/signature skills are no different in damage done for the same time spent.
What I mean is that if you are casting meteor and magic missile, the meteor does more damage on a slower weapon but your signature spells don't do ANY additional damage at all for faster casting speeds. They do the exact same damage with slow and fast weapons given that the DPS is the same. The time between 2 casts of meteor is exactly the same regardless of weapon speed: 4.8 seconds. The DPS of signature/academic skills is the exactly the same regardless of weapon speed assuming same DPS. 2 casts at 100 damage each is the same as 4 casts at 50 damage each, because it's taking the same percentage damage from the weapon. This means for any two items of the same DPS, you get a boost in overall damage done for any period of time, and no additional cost by going with the slower weapon because it makes meteor do more damage, for free.
Side note: There actually can be a small, but not significant enough difference if the casting time between casts of meteor can actually inch out an extra signature/academic spell between it, based off the item. The difference between the damage the extra cast gets in and the extra power of the meteor is always in the meteor (or otherwise high AP spending) skill.
The only two "offensive" skills that the wizard has that don't drain AP significantly fast are like you said Disintigrate, and additionally Arcane Torrent. Everything else does drain it quickly as to where resource manangement does matter more. Which means anyone who uses any of the other 8 "offensive skills" WILL care about doing more damage.
So the question was, given the math and change to weapon speeds affecting cast speed, is there anything you were doing to make faster weapons have more incentive to using them (like changing the arcane power cost based on weapon speed, change the regeneration rate of AP based on weapon speed, making signature spells without runes and passives give AP back like other classes resource generators) or if this was an intentional design, and slower weapons of equal DPS just are, always better (until using golden runes/passives finally hurdles over the breaking point late in inferno) or is this still something that you're looking into and need to work on?
I'd invite you to look more deeply into the math regarding why slower weapons are better, someone started a thread in the Diablo 3 Wizard forums: http://us.battle.net/d3/en/forum/topic/3424795605
-BlizzCon Question Asker Guy
Okay so first I'll start by saying that all of your math is correct, (except for the one exception case that I'll mention later). The conclusions are all based on information you have available, so mostly I'm going to mention a few things to consider, and then I'll fill in with additional information to complete the picture.
First, a few qualitative comments:
Yes, your build absolutely matters. Some builds may be well designed to favor 2-Handers, and some may favor 1-handers. So the general statement of "The correct weapon depends on your build" overrides everything else I write.
Additionally though, two general rules of Diablo weapon speeds still applies - spilled damage matters, and speed matters for combat effectiveness. In WoW, you might use a 1.5 second cast spell over a 2.5 second cast spell because you simply can't afford to stand still that extra 1 second. How many spells in WoW do you cast purely by virtue of them being instant cast or castable while moving? In Diablo, virtually every spell is working off of your weapon speed, and the need to be able to quickly move 1/10th of a second sooner sometimes matters. Spilled damage matters too. Many aspects of Diablo involve fighting hordes of small monsters. When a monster has only 150 health, who really cares that you hit it for 300 damage instead of 200 damage? Either way it's dead. And if it's dead with a faster weapon, that means you can get to the next monster faster. This means that a weapon with a 1.3 speed that can 1-shot enemies actually has a 30% killing throughput increase over a weapon with a 1.0 speed.
"But I don't care about these edge cases".
Well first, I would argue that in Diablo, these aren't edge cases, they are a core part of the gameplay that come up all of the time.
HOWEVER, for those who are insistent on maximizing theoretical DPS and AP usage, we've decided to cover you anyways.
First, straight up. all things being equal, 2-handers do more damage than 1-handers. This is pretty obvious, but I want to confirm and validate this. The reason it's important to call this out is that all the calculations assume "for any 2 items of the same DPS". But that's not a great starting point, because for any two comparable items at any given level, 2-handers do at least 15% more damage than 1-handers, and in many cases 20-25% more.
To put it another way, many of the posts in the linked thread make an assumption that two weapons are equal DPS. This assumption is flawed - what you really want to ask is "For the theoretically best 2-hander in the entire world (even though I'll never get one)" vs. "the theoretically best 1-hander in the entire world (even though I'll never get one)".
However, what you choose to put in your off-hand, should you choose to wield one, matters.
First, no matter WHAT you use, you are getting a bunch of extra stats. In addition to DPS from Attack and Precision, you're getting whatever other item stats are on your offhand. So you're trading off a theoretical Arcane power efficiency boost for the stats of an offhand.
Furthermore, if you use a shield, you're getting a big armor boost. If you haven't played Diablo in a while, people easily forget, but a lot of Sorceress players used a shield in Diablo II. For some players there is a "fantasy" of "I don't need a shield 'cause I don't plan on getting hit". The reality is that we don't let you get away with that in Diablo. You get hit. We don't have heal, tank and DPS roles in Diablo, so everybody in Diablo eventually takes damage.
Additionally, if you choose to use an orb, every wizard Orb (and witchdoctor Mojo) comes with +dmg on it. So if your mainhand does 8-10 damage at 1.4 speed, and your orb adds 3-4 damage, then that means you're doing 11-14 damage at 1.4 speed. In many cases the orb + the stats on the orb completely closes the 15-25% DPS gap between 2-handers and 1-handers.
Add on top of that +dmg from your rings and amulets, and currently with internal tuning numbers (this may not be how we ship), but 1-handers + offhand out-DPS 2-handers almost all of the time. It takes a luckily rolled 2-hander to out-DPS most 1-hand + offhand setups if you can also spare some +dmg on your rings and amulets.
Finally, fast weapons are better at fishing for procs. Diablo has lots of very cool proc effects. Chance to gain Arcane power on critical hit. Chance to summon a fetish on spell cast passive on the Witchdoctor. Faster and more frequent casts means more opportunities to fish for procs.
Where does that leave us? Well currently for internal testing of Inferno mode, 1H+Orb is overwhelmingly better. You get more damage, better mobility, more stats, and more proc fishing. 2H gets you better Arcane Power efficiency. If anything I'm currently worried that 2H is too weak. The most likely solution on this front will be to reduce the amount of +dmg found on rings and amulets to reel in the damage advantage of 1H+Orb. However, the value of Arcane Power efficiency varies the more you have to run and move. If you're running and moving constantly, then AP efficiency lets you drop big bombs like meteor and Hydra when you finally get to stand still. Since the amount of running and moving varies from situation to situation, I'm actually fairly happy with where things are.
On the topic of Disintegrate and Arcane Torrent, we're actually currently considering a change to make them drain AP faster, to match the drain rate on all other skills. I haven't decided yet whether it's better for the game for the philosophy on AP to remain consistent across all skills, or if it's cool that 2 skills break the rule. (Ray of Frost breaks it too BTW). I am currently leaning towards having it drain AP faster because although I absolutely LOVE having different skills for different builds, I also think that when it comes to your resource system, having some standardized themes is what makes it possible to design all the OTHER skills/systems that break those rules. For example, standardized "fast weapons drain AP faster" is also what let's us do "Arcane power on Crit" that let's you feel like you're cheating with all the skills.
On a side note, I don't think you actually get any potential DPS increase by being able to squeeze in an extra cast in between casts of meteor because the time of 4.8 seconds is the amount of time it takes to regenerate back the AP cost of Meteor, but it's not like any additional AP just 'disappeared", you still have it. A 65 AP cost spell gives you a 35 AP buffer to pool over multiple casts. So let's say that you figure out your theoretical breakpoint is "6.9 electrocutes in between every meteor" and you think you're going to get an extra cast if you can get that to "7 electrocutes between every meteor". That's not really correct because 6.9 actually plays out as "Meteor // 6 Electrocutes".... repeated 9 times followed by "Meteor-7 electrocutes".
To be even more pedantic, (but I know you theorycrafting folks geek out on this stuff anyways), this has never actually come up as a balancing issue in any of our internal tests because a Wizard never stands still shooting long enough for this to ever actually matter. The truth is that you're going to weave in other skills, or have to spend time moving, or whatever else long before anything in the previous paragraph matters.