On live servers with proper haste KIR build is already 8% ahead of HO in aoe, which will increase by additional 2.5% with KIR reduction to 6 minutes from 7.
Thats a big difference between builds, so big majority of players will just ignore HO.
In my opinion it would be nice to buff HO back to 100% proc chance, instead of current 80%. Not only it will be closer to KIR, but ambush will be pressed more, and ambush PS loop is actually what HO players enjoy, so this will be fun increased also.
I dont see a reason for it to remain at 80% effectivness.