You are required to work a
"40 hour work week" as a foreign teacher at EF Dongguan, and they hold you to
it!Funny thing is that most foreign teachers in China average 20 working hours per week

Why don't you go back to wherever you are from and see how many hours per week you would be working at a full-time job there? I have never worked at EF but while they have a 40 hour work week I doubt you are actually teaching for 40 hours. EF may also have a 20-25 hour "contact week" but a 40 hour work week (where the other time is used for lesson planning, paperwork, etc). This is pretty standard across most training centres in China (and indeed Asia). Spreading misinformation just because you have a gripe with certain people says more about you than EF itself.

Even if you aren't teaching because they don't have enough students, they have
time-waisting duties like Duty Interviewer (usually a 10 hour shift waiting for
prospective students to come in, then you can interview them for 5 minutes. It is a
regular occurrence to have only one or two interviews the WHOLE DAY! What a waist.)

If they want to "waist" your time, which they are paying for, then that is their prerogative. As far as I understand from your rambling post, they are paying you for sitting on your arse to be the Duty Interviewer for 10 hours. Sounds like a pretty sweet deal to me! If my boss told me to sit on my arse for 10 hours and get paid for it, I would jump at the chance. Also, I would not hire anyone to teach English who cannot differentiate between "waist" and "waste". If EF can be blamed for anything is hiring semi-illiterate morons to teach English. Are you even a native English speaker, Steve Parker?

If you become ill, they
require a doctors note, or you are nicked two days salary. No questions. The schedule is
set up where you have a class in the afternoon, maybe for an hour or two, then another
class 2 hours later for two hours. They count that as "only" 3 hours, I count
it as 7 hours that I can't do anything else.

This is probably because of the high number of "English Teachers" who fall ill so very, very often. Amazingly enough they usually fall "ill" after a big night out drinking. It would not surprise me if this "Steve Parker" was such a teacher. If you are genuinely ill, go to the local clinic and get a doctor's note, surely that is not too much to ask and anyone with brains would do it if two days' salary was on the line (which I doubt is actually true). The whole thing about the hours is quite standard across all training centres anywhere and that is the nature of working at a training centre. If you don't like it, find a job in another type of education facility, don't bitch and whine on an Internet board.

These
managers manipulate others, and I believe take advantage of blokes who don't have a
college education. The Visa that they obtain is the preferred Visa, but you can, and
most do, teach in China without it. Don't let them fool you. I have, and many of my
friends have taught using other visas.

If you do not want to be taken advantage of, here is an idea, go back home and get properly educated so that you actually meet the minimum standards for teaching English in China. Working on a tourist or business visa is illegal. Just because you and your buddies do it, it does not mean that it should be done and you do run the risk of being fined and deported if you do so. It is unprofessional scum like you (and your buddies who replied to this OP) that give all decent English teachers who do the right thing a bad reputation.