i know this is a necro, but this topic comes up first when you google this addon, so for people looking for information:
if this addon doesn't fire aimed shot, it might be in conflict with another addon. for me it "worked" only after deactivating YaHT (let's be honest, if you use OBH, you probably have no use for YaHT anyway).
This addon does not take your auto shot cd/cast time into account in any way (at least that's what it did when i tested it today, with no other addons active). it will start casting aimed/multi as soon as it comes off cd, meaning all it does is the same as this macro:
/cast Aimed Shot
/cast Multi-Shot
That means this addon is entirely useless.
it will also effectively make you get a lot less auto shots off over the course of a boss fight, because it will clip auto shots, so it's a straight up dps loss, so... wait, sorry, that means it's worse than useless.
steer clear of it if you want to play the hunter class properly, install YaHT instead and read something like this to git gud.
Cheers.