Hello all. First time poster here, but I've been a lurker since coming back to WoW for MoP. I want to start by saying thanks Zagam for all the had work and helpful info. I have read a couple posts questioning the significance of haste breakpoints, and I have had the same thoughts myself. So I wanted to make this post to discuss the significance of the haste breakpoints. I am writing specific to warlock affliction spec, but this should be useful for any class/spec looking to hit breakpoints for their dots.
First off we know haste breakpoints give more ticks to dots. That is great, but what exactly does that mean? Haste makes dots tick faster. This translates directly into increased dps. It also reduces the duration of the dot to line up with a constant number of dot ticks. Once the dot is ticking fast enough that it can squeeze another tick into the original max duration it does so, and the duration of the dot is pushed back up to the max.
Lets take Agony for example. It has a duration of 24 seconds and ticks every 2 seconds with no haste, so 12 ticks total. As you gain haste that 2 second tick is decreased until you reach about 1.84 seconds. At that point you can squeeze an extra dot tick in (1.84*13=23.92). What this does is essentially increase the duration of your dot by 1.84 seconds, as compared to what it was just before you hit the breakpoint. The key here is that this does not directly affect dps. It can lead to higher dps only because you have to refresh the dot less often so you have more gcd's to play with. And this is only the first breakpoint. Every subsequent breakpoint will add less time to the duration of the dot. The second breakpoint comes at 1.71 second ticks. The third, which many warlocks strive for at 6637 haste, is 1.6 second ticks.
So lets take the case of a player being 1 point below the third breakpoint. This will give you the maximum increase if you get that extra haste point and hit the breakpoint. You would gain about 1.6 seconds on the duration of your agony. So assume a 10 minute patchwerk style fight. If you fail to get that extra 1 point of haste your agony duration will be about 22.4 seconds. 600/22.4 = 26.78 so say 27. You would have about 27 full duration agonys throughout the fight, meaning you would refresh 26 times. Now you hit the breakpoint. 600/24=25. You would refresh 24 times. So in an ideal situation with perfect play and 10 minutes (which is much longer than most fights) you gain yourself 2 gcd's to play with. Maybe that is 2 extra ticks of MG. The same analysis can be done for corruption and UA.
The corruption BP comes at the 4717 mark where you gain 2 extra ticks instead of 1 (I will assume everyone has hit the first just from base stats on their gear). So with a duration of 18 seconds and 10 ticks before the BP, 11 ticks after, the duration changes from about 16.4 seconds to 18 seconds. 600/16.4=36.6 and 600/18=33.3. You gain roughly 3 GCD's.
The UA BP is 6637. You go from 8 to 9 ticks, and duration of about 12.4 to 14 seconds. 600/12.4=48.4 and 600/14= 42.9. You gain roughly 5 gcd's
This gives you a grand total of 10 extra GCD's on a very long (10 minute) fight. This is a significant number, but this analysis also assumes you are manually refreshing each dot every time. It does not consider that some of those refreshes will be SB/SS. It also assumes the fight allows for 100% uptime of dots. Many fights do not. And it assumes you are only adding 1 point of haste to hit the breakpoint. In the case where you are trying to add a few hundred, or even a thousand, haste then the difference between the pre-BP and post-BP duration will be less than the maximum gain. This will mean you gain even fewer GCD's by hitting it. So it is up to the individual player to decide how much effort it is worth to try and hit these breakpoints. My personal feeling is that in a realistic fight situation these extra GCD's will be absorbed by the mechanics of most fights, the less than 10 minutes time, and the less than perfect play of human beings. I also feel that if your dots hit harder because you didn't sacrifice mastery to try and hit a haste breakpoint then you will probably be better off in situations where mechanics do not allow 100% uptime.
Please discuss, analyze, and tell me your thoughts. And if you find error with my analysis please don't hesitate to point it out. Also I did not consider the effect pandemic will have on this, but if you consider that after the first recast you are probably refreshing on average every full duration of the dot (i.e. 24 seconds for agony, etc.) then it should not affect the analysis. I also ignore the effect of stat snapshots. More ticks of an empowered dot does mean more dps. An analysis of this aspect of extra dot ticks might prove my thoughts wrong. However if you consider that you are only gaining 1 tick from a breakpoint, and that every dot refresh is not going to be empowered, I think this will be absorbed by the added dps of having all dots tick harder with more mastery.

I was having trouble finding a good reference for what I wanted to have my haste at given how weak it is for fire right now.
The only reason for this was DoT breakpoints being affected by it, and I had quite a bit of trouble finding a good reference.
Figured I'd share what I found here.
https://docs.google....xZmFYa0E#gid=39
I found the above spreadsheet >Here<
I'd like to note the tabs at the bottom showing a detailed breakdown of the haste breakpoints for other classes as well.
I hope you guys find it as useful as I did.
I'd also like to request a haste breakpoint table being added to ever-expanding mage guides.
With Love (except for you, vish),
~Sage