The Human Resources Department would not only recruit employees and see to their welfare (a happy criminal is a productive criminal), but screen personnel in ARGENT's front companies for the right temperament and motivation to be inducted into the true corporation. Human Resources would likely also be the vehicle for "subcontracting" manpower from other criminal groups like VIPER and mercenary supervillains. They could also be responsible for acquiring the many human subjects ARGENT experiments on. I could even see Human Resources functioning as a kind of internal secret police, monitoring employees' loyalty as well as their productivity.
I've actually worked for a company that had a Human Resources Dept. that was very much the 'Secret Police' i.e. monitoring web activity, actually enforcing a dress code, etc. so you're analogy rings true. I could see unsuccessful ARGENT employees becoming lab rats as punishment.
Referencing my earlier mention of ominous threats...
"I'm afraid you've made too many mistakes, Director So-and-so. Human Resources has been notified. Expect your reassignment to be...unpleasant."