Really, zerker is a high ceiling class? Holding mouse 1 and using WASD is not hard at all. Besides, I absolutely suck as zerker and have a really ****ty computer, yet I can hold my own as a zerker. So yeah, that has such a high skill ceiling.....
Hmmmm. You "absolutly suck" at zerker, but can "hold your own". That makes absolutly no sense what so ever, and qualifies as a contradiction, as you absolutly can't both suck and be able hold your own.
If zerker is nothing more than holding mouse 1 and using WSAD, then camping is nothing more that using mouse 1, and R.
Zerkers have to know the map inside out and backwards, have to control the spawn, prioritize targets, have constant situational awareness, and deal with muliple Zeds at the same time.
Camping teams huddle up in a small room, funnel Zeds into a small area/opening, point and click.
Support is as easy as point and click? Really? That's a joke there and I'm not even gonna touch that. Ok yes, the melee alt flinch/hunting shotty trick is a little cheap, but even so, you can legitimately kill a 6 man HoE scrake with 3 pump headshots and an alt hunting to the face if done right, OR 5 aa12 headshots and an alt hunting shot. If you are wondering how I mean a "legit" kill, it's not the backflip kill, it's the standing decap kill where the animation doesn't even show right, where they hunch their head for a second then walk around before falling over dead.
The AA12 and Hunting shotty is more than enough to kill a Scrake, it's not even a challenge, as far as the FP, 2 nades, and then the AA12. Big groups of zeds are taken down with 1 or 2 shots as all the Support weapons kill multiple zeds with a single shot, and aiming is not really a requirement, just point in the general direction, and click.
Medic takes no skill whatsoever, pretty much, shoot 2 darts, drop medic gun, pick up, shoot 2 more. Oh, if you're talking about body blocking as a medic, ok, how hard is it to use your body to make a FP move to the wall? Ok you're on an open map? Ok how hard is it to move in front of a FP that's raging to take the hit. Btw, if it's a raging FP, it's better for the Zerker with his GODLIKE damage resistance to take that hit anyway.
Medics have to move around a lot and hit players that are moving, if the Medic is supporting zerkers, then it takes darn good aiming, and they also have to deal with stray zeds while healing and moving.
Firebug is a tougher perk to play well, but if you are smart and buy spare flamethrowers and mac10s you can easily survive up to wave 10 and on without having to be stuck using just 9mm at the end.
If the player is good, then spare weapons are not needed, if the FB is using so much ammo that he needs spares, then that player sux.
Demo has ammo problems? Are you shooting at single zeds? Wait till you get clumps of 3 or more and shoot then. Scrakes? Be smart and DON'T SHOOT THEM!! FPs? Ok a 6 man HoE FP dies to 3 nades and 2 M32 shots OR 2 nades and 3 M32 shots OR 2 pipe bombs, OR a pipe bomb a nade and an m32 shot. Don't even get me started on how easy Pipe bombs make HoE if you have a competent team that can throw you extra cash every wave. When you can put down 65 pipes at once on a map without having them blow up there's something wrong. (Don't believe me, I'll show you screenshots with upwards of 40 - 50 spread out on "pipe walls" or "pipe halls" to fall back to if anything goes wrong.)
It does not change the fact that demo has limited ammo, and your senerio does not happen that often.
And once again, I'll say the same quote I've said 6234234234 times, it's not the perks that are OP, it's the players that make them so. Zerker just happens to have the most forgiving learning curve because they have godly restistance that can protect them and allow them to engage any and all zeds.