Add-on recommends flagellation at the beginning of combat, however it lets the debuff fall off without consuming the stacks for the haste buff.

https://pastebin.com/qeAN4X3y

Will take a look.

Should be addressed in next build, but I'd watch it closely -- the default priority puts stealth and CDs above Flagellation Cleanse and there's some risk that you'd miss the 2 second window.