I was just running some tests on attackspeed and dots, and the TL;DR is that Attack Speed is a useless stat for dots.

I was able to add 25% attack speed between a ring and an amulet without effecting any other stats. I had no other bonus attackspeed, but I was wielding a pretty fast ceremonial knife to start with.  I did all my testing on the Zombies outside Tristram in hell.

My stats, off the character sheet: 
Damage: 1273.63
Damage increased by intelligence: 870.00%
Damage increased by skills: 0.00%
attacks per second: 1.4
Critical Hit chance: 5.00%
Critical hit Damage: +50.00%

Equipping my two attackspeed items changed:
damage: 1592.04
Attacks per second: 1.75

First I checked locust swarm.  I didn't record the order of ticks (which seemed random), only the number of ticks of different numbers.

Without attack speed I saw:

 - 15 ticks, 11*200, 4*240, 1*40 = 3200 damage total
 - 15 ticks, 5*240, 10 * 200 = 3200
 - 16 ticks, 4 * 240, 1 * 40, 11 * 200 = 3200

With attack speed I got:

 - 15 ticks, 5*240, 10 * 200 = 3200
 - 15 ticks, 2 * 240, 1 * 120, 12 * 200 = 3000 (user error?)
 - 16 ticks, 3 * 240, 1 * 80 = 3200
 - 16 ticks, 1 * 240, 1 * 160 = 3200

Haunt was a little less clean.  Most ticks were 213, but the increments were all still in multiples of 40, and it seemed like the extra 3 damage varies between the casts with different numbers of ticks.
Without attackspeed I got:

 - 23 ticks, 5*255, 18 * 213 = 5109
 - 24 ticks, 1 * 43, 4* 255, 19 * 213 = 5110
 - 22 ticks, 10 * 255, 12* 213 = 5106
 - 23 ticks, 5 * 255, 18*213 = 5109
 - 23 ticks, 5 * 255, 18*213 = 5109
 - 24 ticks, 4*255, 1*43, 19 * 213 = 5110

with attackspeed:

 - 24 ticks, 1 * 83, 3 * 255 = 5108
 - 24 ticks, 1 * 43, 4 * 255 = 43 + 1012 + 4047 = 5110
 - 23 ticks, 5 * 255 = 5109
 - 23 ticks, 5* 255 = 1265 +  3834 = 5109
 - 23 ticks, 1* 128, 7 * 255, 15*213 = 5108

Result: I'm nearly sure I just miscounted that one locusts (counting two different things while kiting even slow moving mobs is harder than it looks :/), and there's what looks like rounding error with the numbers out of haunt, but we were looking for a 25% damage increase, and it's just not there.