His insta heal is big, but only when ally is in his circle. Firstly you and "your allies" should pay attention to "his allies" and them occupy with something. Then when Grover is left alone it's your chance to challenge him on solo fight.

Furia is mainly backline high damage supporter that should be used more to defend oneself. She shouldn't be atacked directly because of damage and beams. The best way to counter her is force her to waste all skills, or atack from distance.

As long as Koga has at least one dash it's impossible to use beam on him. To counter him you should always stay close to one ally with CC ability. Bait him to use all his dashes and stun him that he can't counter you alone.

Without your ally staying close and keeping distance you don't have any chance against Zhin. He can counter your Beam just with Whirl and counter you Wings of Wrath just with Billow. Zhin is danger from short distance so just be sure he is far away.