It's a 3 sec reduction that gets effected by haste they said so most likley could be 5 sec or moreWith Dire Frenzy / legendary shoulders, even with 2 stacks you get countless DF CD wasted, since its only optimal to use the skill to refresh the pet buff, thats the whole point of this talent. I have the shoulders, i'm pulling 800k on Krosus mythic with it and i cannot count how long i've sit on 2 stacks of DF waiting for the pet buff to reach 1s so i can refresh it. DF is all about pet buff management, not how many times you can use it in a fight.
Now, if you have a 5s CD reduction, you most often will be able to use DF on cooldown without the worry of losing the stacks on pet, since the buff lasts 8s on pet, one single 5s reduction proc during that period would make it viable to just spend the DF charge at will.
OWTP might be mandatory, but the legendary shoulders wont, since you will now be able to most likely just spend that DF without caring about the pet buff... 100% chance to reduce 5s on DF? Sign me up, i'll delete my legendary shoulder in a live stream if this happen.