How do proc rates work? Is it a percent chance per swing, or procs per minute? If its per swing, I can definitely see there being a benefit to getting an FBSS.

Well... sky belts have better stats, but less haste. For anybody just doing dps the FBSS is better, and even tanks might prefer it a lot of the time when just doing relatively easy trash I'd think.

Procs aren't based on swing rate.

Haste does not effect proc rates.

some belts like the warrior (Contention) and the Monk belt (Tranquility) and rogue belt (Transience) are all 21%.

The hybrid belts and the bard belts are 16%.

It is a pretty accurate overall chance. I took spawn percent chance times drop rate. He's off by less than a half a percent.

BOOYA