Is it normal for sys admin tasks to be put on helpdesk?

It’s not that abnormal, and it’s a good way to learn (it’s how I did, I was doing high-level sysadmin tasks while technically a level 1 helpdesk tech), but it’s also dangerous. Most helpdesk folks don’t have the knowledge and experience to understand when they’re doing something harmful or insecure or both. I’ve seen a lot of helpdesk-led migrations, server decoms and network changes go really, really wrong. And that’s because having someone with a year or two of experience do sysadmin-level tasks is like asking someone who has played Call of Duty a couple of times to lead an SF raid in Somalia.

As someone points out in the comments, these sort of tasks should only be worked by helpdesk with the close guidance of those more experienced. Otherwise, disaster is not just likely but certain.