http://wiki.bluegartr.com/bg/Climactic_Flourish
It basically makes the main hit of Rudra's (most of the damage) a crit with +20% damage.
If a THF had 120 DEX in their Rudra's gear and capped fSTR with 225 TP (Fusetto +2 and Moonshade), they'd get 549 crit base damage after fTP, and then another 120 crit base damage from DEX for a total of 669.
If a DNC has 120 DEX in their Rudra's gear and capped fSTR with 225 TP (same setup), they'd get ~659 crit base damage thanks to the AF3+2 head.
So it gives pretty much the same damage bonus to Rudra's that un-enhanced Sneak Attack gives. I can't tell what enhanced sneak attack gives, because I can't find any darned testing on it. xD