It's been there for a while. Concussive is really just a hunter version of a delaying tactic. Many argue it's merits around here and I'm kind of the sort that finds it coming in handy from time to time PvP. Multi is your main damage dealer against PvP groups and usually hits hard even 1:1. So multi > Concussive, with the shorter CD, it's made even better but it's hard compare the two shots, one is offensive, the other defensive. They are used differently and for different purposes.
I'm working on my 3rd S3 piece now and hope to have a fourth, but I may go S2 on it if it goes down to just gold when S4 comes out. The one second bonus is certainly worth some gold to get. I'll probably PvP & Raid in a hybrid gear set until I get enough of each to change around. I want that one second drop though. It's basically an extra multi-shot every minute. That's significant dps.