This may be somewhat of a moot point because I generally prioritize secondary stats (after hit/exp) crit > mastery > haste, but I'm rather curious about haste and potential gains versus actual gains, and I'm hoping that better understanding this will inform my play and not just my gearing. Also, this is as a SV hunter, though it is still translates to BM and MM.
As I understand it, haste decreases time between auto-attacks, decreases cast time of non-instants (e.g. cobra shot), and increases passive focus regen. [I don't think it affects pet attack speed, but I could be wrong. I believe it also has a breakpoint where it, 50% of the time, adds an extra DB swing.]
I understand that the passive effects (quicker auto-attacks and increased focus regen) are easy to reap the benefits of. My confusion surrounds the value of decreasing the cast time of your focus regen shot. In a vacuum, that sounds great, but with a 6 second cd on your signature shot, how often does that decreased cast time translate into an extra shot/extra dps?
After an explosive shot (barring LnL procs), you have 5 GCDs to work with. You don't want to be casting CoS when ES comes off CD. So let's say you get off 2 cobra shots (with 1.7 second cast times) and an AS. Assuming 0 latency, instant response time, etc, you have 0.6 seconds before an ES should be fired. What good is that 0.6 seconds? Do you queue up another CoS and just delay the ES? If not, would a 1.9 second cast time have been just as effective as far as getting the most out of your GCDs?
I understand there are times in a fight when it may make an appreciable difference (under bloodlust/heroism or rapid fire, getting a LnL proc during a CoS, etc). But my thoughts are that it may not be meaningful in a default setting. And even if you get below 1.67 seconds, how often are you going to be casting 3 CoS's in a row? (It seems like it would require you to deplete most of your focus a lot more.) Ofc, if 1.5 seconds becomes doable in higher gear, I can see that being pretty strong.
Not even looking at AoE situations where mastery is clearly better than haste for SV, I feel more comfortable with mastery since it's a flat increase. Haste's value, in my understanding, diminishes more quickly with less-than-perfect play than mastery does.
TL;DR-Is haste less valuable than it sims for most players who don't play with the response time, foresight, and precision of spreadsheets?
Related (and perhaps the cause of some of my confusion), how much time are you willing to push back an ES to get off a CoS (versus sitting on your thumbs waiting for the CD)?