I don't think the SSG are actually fighters. Rather, I think they are simply a science research organization within the marines. The SSG produces weapons of mass destruction that regular marines can use in order to beat people significantly stronger than them.
That's why they are sending Coby to take out hancock, why they literally sent fodder soldiers to take out weevil, and why they are even attempting to take out Mihawk.
Like for example, what if Vegapunk found a way to fit the pacifista lasers into a gun that can be given to a normal marine soldier. All of a sudden, marine fodder have become far more deadly. If you can give fodder that level of firepower, you could easily take out a warlord with a vice admiral and a couple of marine captains.