When I worked for HR we were always run off our feet, because employees like to moan about everything 
We dealt with attendance, sickness, grievances, disciplinaries, recruitment, interviewing, reference checks, pay reviews, appraisals, headcount, employee records, termination of employment and so on. There is a lot of paperwork, filing - but a top HR person has to be up to date on employment law, and deal with some pretty sticky situations. We had about 300 staff, payroll, me and my boss. Kept us busy. We used to have factory managers just firing people without using the proper procedures and all sorts.
We used to get the most amazing letters from employees - moaning about their staff/boss. Long diatribes ending with "... but it was the way she said it" and "he phoned in sick, but then I saw him clubbing in town" etc. 
I had to deal with a poor alcoholic woman once, who had been drinking bottles of vodka at work. She fell down the stairs - it was awful. She rang me, clearly drunk and very tearful. We had to terminate her employment of course (gross misconduct), and I felt so awful about it. I often wonder about her, hope she's ok. This was about 15yrs ago.