The game was never meant to be easy. In KF1, it was the quantity of shambling horrors and the special abilities that killed a team. In KF2, it got more fast paced. There are less zeds and they come at you faster, allowing a ten wave game to take half an hour. The last 5 rage mechanic is to end the wave without everyone searching for free ammo and guns. That's what the trader minute is for. This was to replace the teleporting zeds, which was just stupid, especially when the zed type switches. I've never had problems with the last 5. Either one guy was soloing since everyone else died before the 5 zed mark, and if he made it that far, he usually made it the rest of the way, or the team survived and took care of the incoming stragglers. But as it is a problem for others, and there are some points beyond, "*Whine* its harder *Stamps foot*." Here is my idea:
Zeds instarage at the 5 zed mark. Not permarage, but insta. Since only the fleshpound can un rage, they won't stay raged, and anything spawning in won't be raging. When no zeds are raging, instarage again. This allows zeds joining after the instarage to instarage without overwhelming and it makes the fleshpounds rerage. And if only fleshpounds are left, when all are yellow, they all turn red. This forces you to keep one raging to keep the team alive. And if a single fleshpound is left, when he unrages, he rerages. To throw you guys a bone, everytime the fleshpound rages, he has to do his rage animation, giving you players some time to make a run for it or put bullets in him. Its not permarage, but constant reraging.
On another note, I like the idea of getting rid of the zed counters. Some servers in KF1 had that and those were fun. Make it a server option or something. I also think they should add back the kill counter so we all can tell when a large zed is dead and who got it.