Most of the dmg spiking from thfs is the forced critting... really brd/thf could put out almost as much assuming they can get similar levels of dex, crit dmg and attack.

Dncs can actually do it themselves just Climactic Flourish has a 1.5 minute recast (though it does add 20% to the critted hit) and also adds stat dmg on similar to sneak/trick attack. Though Striking flourish can also be used and only has a 30 second recast though it's only 50% chance to crit