Focusing on the haste portion, the number represents a breakpoint for 2 extra ticks of renewing mists. With or without the haste buff, one needs a total of 16.6% haste to get that extra tick.
The other spells which could benefit from haste are enveloping mist, with breakpoints at 8.29%, and 24.92% and Zen Sphere (which I don't use) with breakpoints at 6.24% and 18.73%.
So the mathmagicians have figured out the sweet spot is aiming for the second tick of renewing mists. I have little doubt that their calculations are correct.
But for nearly every 10 man I've run, I've NEVER had spell haste buff present. I've even had runs with THREE hunters, and NO SPELL HASTE. As an aside, hunters, keep a spore bat at the ready.
I know in 25s you're likely to have either a spriest, boomchicken or ele. But in 10s spell haste buff that seems consistently missing. Expanding spell haste to other classes is a subject for a different thread, and there are plenty.
Since we have fixed GCD and the ability to layer in instant cast spells to our main channeled spell, haste has next to zero value to us, other than those ticks.
Without the spell haste buff, it feels impossible to get to the second break point, at least without doing something that feels really stupid, like losing too much spirit. I already feel like I am running on fumes.
My hybrid question/statement is, I guess the best thing to do is reforge to the first haste breakpoint, followed by crit. With my current gear, if I proceed with that reforge strategy, I will trade about 7.6% of haste, which is essentially worthless without the spell haste raid buff, for an additional 3.4% crit. The net effect on mastery would be negligible, as I would mainly be changing mastery-to-haste reforges to mastery-to-crit reforges. I mention this because healing spheres from gift of the serpent still make up some 8-10% of my total healing, even after having reforged mastery to either haste or crit.
How are other mistweavers reforging their gear for groups where there is no spell buff?
Thanks for your thoughts. Extra points for people with actual experiential information.
And yes, it will all change come 5.2%.