It interrupts there abilities that they are trying to use and it works against Charge/Leap/Throw saber or whatever you want to call it and by using Unload it prevents them from running up on me along with all the other utilities I have. Pyro is another great spec with hit run kiting abilities.
Mercs were lacking without a interrupt ability and I have seen a great deal of improvement with the new changes.
The only complaint I have is if only rocket punch maintained the knock back affect with the immobilized effect. Other than this I am happy
What more do you want but I will give you this "Mercs do have a higher learning curve than any other class out there". It truly is a advance class to play in terms of mechanics and situations and I like that about this class. I wouldn't of played it for so long if it was pure easy mode.