A typical, non-modified, Psychic Scream lasts 8 seconds, so this reduces the amount of time between the end of one scream and the beginning of another. However Psychic Scream can still be resisted, dispelled, or other wise countered in PvP, making its use as temporary crowd control limited.
Paired with any of the PvP gloves (such as [Cataclysmic Gladiator's Mooncloth Gloves]) the cooldown can be reduced by a further 3 seconds for a potential cooldown of 23 seconds, greatly increasing the frequency with which the spell can be used.