Because Josh Hamerick thought it was frustrating to play against. Lol, that is the reason it was nerfed. One devs opinion. It didn't need to be nerfed at all. Now that it was nerfed, other class perks, (titans, warlocks, and hunters), gun perks, and some exotic armor perks took on the same nerf as hb. Such a fail on bungies part. Maybe next time they won't release an unfinished patch before the test and finish it.