Here is a Copy/Paste from an earlier thread. Don't know who to credit , but the logic is solid. Im just not so sure about ditching my shield.
"assuming weapon A is a fast 1 hander with 500 weapon damage but attacks 1.5 times per second. with off hand which has 167 damage increase. Taking attack speed into account, 1.5 *167 = 250.5 (give or take), and 500 *1.5 = 750, giving you a total of approximately 1000.5 dps.
Weapon B is a slow 2 hander with 1000 weapon damage but attacks 1 times per second. giving you 1000 dps (same dps).
Weapon C a semi-fast 2 hander with 800 weapon damage but attacks 1.25 times per second, giving you 800 *1.25 = 1000 dps.
They are all the same DPS but have different attack speeds.
All your spells scale their damage on your WEAPON DAMAGE not your weapon DPS. so lets give it a go; assuming with no other gear (all gears will scale equally with all weapon types, so it doesnt matter).
1 cast of un-runed arcane orb from weapon A deals (500+167) * 1.75 = 1167.25 damage. (35 AP cost)
1 cast of un-runed arcane orb from weapon B deals 1000 * 1.75 = 1750 damage. (35 AP cost)
1 cast of un-runed arcane orb from weapon C deals 800 * 1.75 = 1400 damage. (35 AP cost)
in the time it takes weapon B to cast 2 times, weapon A can cast 3 times.
Weapon A damage done would be 1167.25 * 3 = 3501.75 damage (35 * 3 = 105 AP cost)
Weapon B damage done would be 1750 * 2 = 3500 damage (35 * 2 = 70 AP cost)
As you can see, this already proves the "myth" of AP consumption. AP cost is higher the faster your weapon is.
To make a clearer example, assuming you have an AP pool infinitely large enough to consecutively cast arcane orb for 20 seconds:
Weapon A can cast: 20/0.666667 = 30 times
1167.25 * 30 = 35017.5 damage (35 * 30 = 1050 AP cost)
Weapon B can cast: 20/1 = 20 times
1750 * 20 = 35000 damage (35 * 20 = 700 AP cost)
Weapon C can cast: 20/0.8 = 25 times
1400 * 25 = 35000 damage ( 35 * 25 = 875 AP cost)
Lets not mention spells like blizzard do NOT benefit from weapon speed or IAS at all and benefit solely on weapon damage.
as you can see, all the weapons deal the exact same amount of damage at the given amount of time, however, the AP cost is increased for the faster weapon.
IAS in gear always helps (as i have stated in my first post which you chose to ignore for some reason), however, IAS in weapon doesnt, its fake damage for the most part. IAS in gear will scale equally with weapons A, B or C, but its best applied with weapon B (which was what my main post was about), as you will hit hard and fast, rather than hit fast but waste your AP for the same amount of damage.
Lets not forget the main advantage of using a slow 2 hander:
we kite.
When kiting, you cannot sit and cast spells, lets assume you need to run for 2 seconds before you are free to cast a spell:
with weapon A, you will be doing 583.625 damage per second, with 66.67% DPS loss
with weapon B, you will be doing 875 damage per second, with 50% DPS loss
with weapon C, you will be doing 700 damage per second, with 60% DPS loss
this gets amplified when say, you can afford to turn around and shoot every 1 second (this is a rare case, as you seldom get the chance to shoot this freely unless kiting slow mobs):
weapon A doing 1167.25 damage per second, with 33.33% DPS loss
weapon B doing 1750 damage per second, with 0% DPS loss
Weapon C doing 1400 damage per second, with 20% DPS loss
there is almost no advantage with going with a fast weapon other than to cast faster, which can be eliminated by having IAS in gear which makes your slow weapon cast faster too.
Fast weapons are beneficial when you have reached a certain attack speed plateau where you can cast multiple times where a slow weapon would have been able to cast and still do more damage (example is a 2.00 attack speed weapon which has more than 50% of a 1.00 attack speed weapon's weapon damage). And of course, fast weapons work best with critical mass, other than that, a slow 2 hander will always beat a faster weapon"