1. It's easy to dodge fireballs if you stay outdoors, keep distance and stay alert. Never stay at one spot. Keep moving. You don't have to run far though, you will dodge stuff even if you moved a little bit. So shoot->move->shoot->move
2. Their suicidal move is extremely dangerous, so again keep distance and stay alert. You have to know what's happening 360 at all times.
3. Their friends EDARs are easy to kill, just aim for the red dots with anything stronger than 9mil + accurate.
4. Have balanced team. 6 zerks will have a hard time with this wave. Bullet classes are the best against them. Especially SWAT and GS.
5. Always go for the weak points! It's the key advice really. You will have a hard time getting through their overall healthpool. Also they will try to suicidekill you.
6. Spread out. Because a. they have aoe, and b. it's much easier to hit their backpacks (the weak point) when they are going in different directions.
7. During the Halloween event their backpack isn't the easiest target though. But they have another weak spot nowadays - cannon in their chest. They open it up when shooting fireballs. So all you have to do is to shoot the husks that opened up and about to shoot. There will always be one, lol.