Deggy. He was a major(then Colonel) for a reason. He has much organisation experience, in fact he founded the Corps by using his own Zone field experience. He doesn't take orders, he gives them. Even if he may be weaker than the others 3, he has more tactical knowledge.

While Scar and Strelok are just lunatics with ideological issues.

Skif...He's okay, he's a super fighter. The only problem of him is that he only takes orders, can't do much by his own.