What purpose dose overhead blow ablity on chosen serve?

[TenTonHammer]

So overhead blow is a 40ap costing "undefendable attack" that as far as i can see still gets reduced by armor?
for a class that in my opinion suffers from ap cost issues this seems like a really underwhelming ability especially when i compare it to the KoTBS precision striking ability which is pretty much the bread and butter of the class

(maybe im just doing it wrong)

Does this ability every become good/useful especially when it seems like ravage is the better alternative?

[Azarael]

"Undefendable" means that the ability will never be subjected to total mitigation defenses (block, parry, etc.).

Ravage sucks in T1 against most targets due to high Spirit resistances.

[Luth]

An "undefendable attack" is an abilitity that can't be avoided through block/parry/disrupt/dodge. Thougness, armor and resists are normally calculated.

Edit: too slow