Here’s some notes from Sigma, one of the developers, on the changes to Breath of Sindragosa so far on the PTR:
We agreed with common feedback that Frost DK, overall, had too high a portion of open GCDs in a steady-state rotation. When this happens, it’s generally a problem with a spec’s resource economy, and the baseline buffs to Runic Empowerment and Frost Fever resource generation were meant to address it.
But Breath of Sindragosa poses a further problem. A Breath that spends (for example) 300 Runic Power is, in a single button press, removing 12 Frost Strikes from the future. In other words, every 2 minutes, it creates 11 open GCDs that otherwise wouldn’t have been there, which is a huge amount. Across all classes, we try to keep an eye on variations in rotation pacing caused by talents—including cases where a talent causes a large deviation in resource economy or GCD utilization—and Breath is a big outlier. And, in all this, we’d prefer to preserve Breath’s signature resource-drain mechanic.
The first solution, giving increased Runic Empowerment proc chance during Breath, did return resources to the rotation, and did so during Breath. While this correctly targeted the talent (Breath was draining resources, so Breath should put some back in order to mitigate the pacing problems), it was the wrong time to give back resources. Even though Breath itself sucks resources away, players shift all possible resources into Breath, because this is the clear way to optimize the use of the talent. Resources can be shifted into the Breath window using ERW, Horn, and simple pooling, with the result that adding more during Breath itself actually overfills it.
So the goal of the current change—Breath returns Runes at the start and end—is to make the Breath talent add resources, but to do so outside the Breath window. Even the Runes at the start are effectively “outside” the Breath window, because they counteract 2 Runes’ worth of pooling that otherwise had to be done to play Breath optimally.
As always, changes are subject to further revision, but this might give some insight into the process for making surgical changes to address specific problems.