Originally Posted by
Meiffert
It doesn't make a difference whether the Whispers buff expires in the middle of the GCD, or closer to it's start or end.
With 0 haste, you only have 2 GCDs in the buff window, which means, you have to go TV - something - TV to get the buffed TV.
To get 3 GCDs, you need 12.5 % or more, with that, you can go TV - Blade - CS - TV or TV - WoA - J - TV etc.
To get 4 GCDS (so that you could do TV - CS - CS - J - TV or similar, you would need 50 % haste, which is not achievable and probably wouldn't be worth it to go for it anyway (haste is somewhat devalued at that point).
During Crusade, you have extra 52.5 % haste, which easily puts you above the 50 % mark. The next one (5 GCDs) is at 87.5 %, which is 35 % unbuffed. Not only is that amount hard to achieve, it's also unnecessary, because you generate more than enough holy power with the 4 GCDs 50 % breakpoint to have full uptime on the Whispers buff anyway.
TLDR: With the cloak, there is a high incentive to reach 12.5 % haste, but after that there is no reachable breakpoint to worry about.