I made some changes to my simulator that people might be interested in. You can now input passive haste effects. Also, I've improved (I think) the way flurry is tracked. I still need some testing data about flurry uptime to tune it a little, though, if anyone's willing to help.
Using the new haste feature, I did some very basic testing with my mod. Starting at a normal baseline (2200/25%c/22%h/2x2.6 speed weaps), I added haste in 1% increments to 10%, then 5% increments thereafter to 60%. Pretty interesting results. Basically, my results agree with the Euro forums results. Haste is good until you drop your flurried weapon speed below 1.50, at which point it becomes a nightmare. As soon as I went below 1.50 weapon speed, damage dropped a lot and didn't recover to over-1.50 levels until roughly 1.41. (For these weapons, about 44% haste through about 55% haste.) Aside from the discontinuity at 1.50, the slope is about 0.66%/%; i.e., 1% haste should give you about 0.66% dps boost.
Graph:
As always, my model is imperfect and may have significant flaws. Let me know if you see flaws that call these results into question!
edit: For the inevitable day in the future when this image exceeds its bandwidth:
Haste% DPS DPS%inc Slope Flurried Delay
(from 0)
0 768 0.0% 2.00
1% 773 0.7% 0.651 1.98
2% 777 1.2% 0.586 1.97
3% 781 1.7% 0.564 1.95
4% 784 2.1% 0.521 1.94
5% 793 3.3% 0.651 1.93
6% 795 3.5% 0.586 1.91
7% 803 4.6% 0.651 1.90
8% 807 5.1% 0.635 1.88
9% 810 5.5% 0.608 1.87
10% 816 6.3% 0.625 1.86
15% 841 9.5% 0.634 1.79
20% 869 13.2% 0.658 1.73
25% 895 16.5% 0.661 1.68
30% 917 19.4% 0.647 1.63
35% 946 23.2% 0.662 1.58
40% 971 26.4% 0.661 1.53
45% 927 20.7% 0.460 1.49
50% 951 23.8% 0.477 1.44
55% 975 27.0% 0.490 1.41
60% 998 29.9% 0.499 1.37
65% 1010 31.5% 0.485 1.33