This thread exists as legacy content. As of the 2.4 patch the specific values contained in this thread will no longer be valid.The following is designed to show the benefits of spell haste as they pertain to your mind blast cooldown.
Since no one else in my guild wanted haste gear when it dropped I got it very cheap. At the same time, I was able to farm hearts to darkness solo to make the haste craftables. I hit 160 haste in about two weeks.
For people that can't do this there are some general rules about shadow and haste. Theoretically you can begin to see a bonus with a 5/5 imp MB with 2 points of haste, albeit probably unnoticeable. Every point of haste you obtain while keeping 4/5 imp MB means you are lowering your potential DPS because of an idle MB cooldown while you are finishing a MF cast.
I previously would suggest for people to stick with 4/5 imp MB until they hit about 140-150 haste to see a significant change, but when micro-analyzing the casting rates we can see a benefits across the board. MB will always be higher DPS than MF given the same base spell damage unless large amounts of shadow damage are added in the future with no change to coefficients. Even then you will be running up against the GCD which will result in MF equaling MB DPS at best given current game mechanics.
My philosophy is that overall effectiveness is more dependent on an individual's ability to judge spell priority instead of building a perfect spell rotation. I can't envision a situation where casting faster would end up lowering your DPS given the same amount of +damage. In a worst case scenario it should be equal if rotations end up mismatched.
The stats I have seen and my real world tests have shown a benefit in DPS when strategically canceling a MF after its second tick if a higher DPS spell is available, but this can be very tricky to time since no mods exist that display a second tick line on your cast bar.
Many people I have encountered assume that the 15.8 haste=1% scaled in a direct fashion. The actual equation ensures that you can never achieve more than 100% reduced casting time, so the equation to see your actual cast time after haste is (100/(100+(Haste/15.8))*Cast Time).
Below are stats generated with my ghetto shadow haste calculator, and I suggest you download it if you're looking for a simple and quick way to get basic haste info and its relation to your MB cooldown. Below are some examples different haste levels and their effect on the MF/MB interaction. MB being on or off cooldown is relative to two subsequent MF casts.
31 haste, 2.94s MF, 1.47s MB
5/5 MB off cooldown for 0.41s
4/5 MB on cooldown for 0.09s
62 haste, 2.89s MF, 1.44s MB
5/5 MB off cooldown for 0.33s
4/5 MB on cooldown for 0.17s
94 haste, 2.83s MF, 1.42s MB
5/5 MB off cooldown for 0.25s
4/5 MB on cooldown for 0.25s
122 haste, 2.78 MF, 1.39s MB
5/5 MB off cooldown for 0.18s
4/5 MB on cooldown for 0.32s
177 haste, 2.7s MF, 1.35s MB
5/5 MB off cooldown for 0.05s
4/5 MB on cooldown for 0.45s
199 haste, 2.66s MF, 1.33s MB
5/5 MB off cooldown for 0s
4/5 MB on cooldown for 0.5s
Eureka!
Conclusion: As we can see, even with one Ring of Ancient Knowledge it is possible to lower mind blast's cooldown. 142 is the magic number to achieve a 2.75s mind flay, but you will still have MB cooldown ending 0.13s before your MF has finished. We can see that 199 spell haste is the real magic number allowing two mind flays to fit perfectly within your mind blast cooldown window. Going beyond 199 will potentially add idle time in this specific rotation which wont increase overall DPS.
At the very least this shows that even with one ring of ancient knowledge you will see some benefit from picking up 5/5 imp MB.
My ghetto shadow haste calculator:
tools/shadow_haste_calc.xlsNew Calculator for patch 2.4:2.4 Shadow Haste Calculator
