Void Grip as an escape route isn't effective if your ally can't kill the enemy quickly and you're with low HP, but you can always gain time by going below the suspended enemy since it's an unlikely thing to do. He'll delay to aim and you'll be safe.
If you believe you are gonna have a hard time against Koga, go Power Cosmeum and grip him every time he is near you, having a teammate to kill him while crippled.