Unreasonable Corvus Glaive's signature ability

Fatmeat

One of the signature ability of Corvus Glaive's is to reduce the cooldown time of Glaive. Actually, it is hard to be activated. Considering opponent will use the block and special attack as well as Corvus Glaive needs to block or evade opponent's attack, it isn't have enough to successfully hit the opponent. 30's seems too short and unreasonable.