Sorry but that linked guide is at best catering solely for a niche style and at worst simply idiotic. Furthermore, camping is not impossible on suicidal.
You DO ideally want a beserker. Beserkers are simply put the best class for dealing with the bulk of the horde. Why? Simple, they don't use ammo. Arguably a chainsaw is better for defensive work in a tight area, while the katana excels with space to move, but a skilled beserker can work miracles with either. At least one sharpshooter is ideal too, nothing takes down sirens like they do, and they can keep an easy watch for other nasties like bloats, crawlers and scrakes. It should be noted that firebugs and commandos can also quite easily fill the role of killing things beserkers can't.
Long story short? Team makeup is not an exact science. What matters more is that each member knows their class role and is competent at it. But ideally what you want is 1-2 beserkers, 0-1 medic and 4-5 firebugs/sharpshooters/commandos (I'd say ideally not more than two of any one of those classes).
The beserkers block zombie approach lanes, eliminating clots, gorefasts, stalkers and scrakes. Medics should be right behind the beserker, healing him and popping away at anything threatening to him but weak(crawlers, bloats).
Firebugs should basically be igniting everything that appears then ignoring them, using short bursts of flame and ideally not sharing a line of fire with other ranged classes, since their aim will be spoiled.
Commandos should be eliminating crawlers and bloats, while also generally thinning the hordes of anything they can easily pop the head off.
Sharpshooters should be more or less ignoring anything but their primary targets; sirens, bloats and crawlers. When none of these are present, just use your 9mm to pop heads. Or kill scrakes for sport. They aren't a threat but it's fun getting bemused comments from newbies that think of scrakes as a big tough nasty enemy, then see them dropped in one crossbow bolt.
I haven't mentioned support specialists at all because I don't consider them to be a worthwhile class. The shotguns are close ranged and unreliable sources of damage due to their spread. Grenades and the LAW serve as little more than a smokescreen for zombies, and lack the ammo to be an effective weapon. If a zombie is close, the beserker should deal with it. If it's close and something the beserker can't easily deal with, slap the other ranged classes, because they aren't doing their job.
Fleshpounds should be dealt with by whoever they're after. If it enrages, pour fire into it, if not, ignore it. The real big killer is not the FP itself, but the zombies that get close as a result of idiots ignoring them. Classes like commandos in particular should basically ignore the FP altogether and just keep on killing regular zeds.
So here's my take on the easiest ways to take on the core maps:
Manor (easy): Camp in the caves, the long central cave should be defended by all but one player, who should be at the back defending the rear. Not many zombies come that way, and if they do he can call out and someone can go help him, or cover his role as he deals with an FP. For patriarch use the manor's basement, you can weld the patriarch in easily then kill him.
Biotics lab (easy): Camp the room with two sets of double doors, welding shut the ones nearest the trader. Early on you can camp the corridor outside the doors, giving you a long line of sight down each corridor, just beware of zombies jumping the barricade behind you. Later on you can retreat into the room, and this can't be stressed enough, STAY AWAY FROM THE DOORS. One siren pair covered by a scrake and you're dead. Give the people in the sharpshooter role time to pick off threats before they cause damage. Keep an eye on the welded doors, zombies will probably break through sooner or later. For the patriarch obviously sit in the same room, weld him in, kill him.
Farm (very easy): Two possible strategies to this, both make for an easy game. In both, contrary to what the linked guide says, being in the open is your friend, zombies don't like you having long lines of sight. One strategy is to follow the river bed until you find a place where you have your back to the edge of the level. Now you can't be flanked and can see zombies a mile off. The other strategy is the mobile defence. Just keep the whole team together and on the move, avoid low visibility areas like the plague (corn fields for instance). The zombies simply won't catch you, since this huge open map has nowhere to corner yourself. Use a barn to kill the patriarch, or at a push one of the other houses. I'm pretty sure all of them have doors at each end to weld shut.
West London (medium): The camping location in the linked guide is correct, in the tunnel furthest from the church is the best camping spot, 3 people covering each end. This rates as tougher because you have zombies coming from both ends into an area with no room for retreat. If something goes too badly wrong, you're probably screwed without much chance of clawing it back. The best place to trap the patriarch is in the small police car park outside the far end of that tunnel on the right (where it leads into police station basement). If a sacrificial lamb manages to get the patriarch inside there and get him welded in, you win. Simple as that. The rest of the team will tear him apart through the wire gate.
Offices (medium): I would tend to avoid camping on this level. Being so confined it's too easy for things to go wrong. Instead I prefer a mobile defence, running up the office via the long route (up as far as the floor below the roof), then going back down via the main staircase. Keep the whole team moving along this route and most zombies end up in a train behind you, with the few spawning in front of you swiftly becoming a big red stain as your team ploughs through them.
Foundry (medium): Again I opt for a mobile defence. Learn the map, well, then make a long circuit of the area, avoiding anywhere you can be cornered. Also make sure your circuit is changable. Sometimes you see a wall of hungry undead ahead of you and you need to spontaneously change your route and still return to your regular path soon afterwards. There are a couple of rooms near the foundry itself you can lock the patriarch in for a quick kill, though there is little cover.
So if there's a thread about it, point me to it.
