So, as the title suggests, I clicked Remove in the discover software centre for VLC but it told me it needed to remove hundreds of packages (the list was endless, and included vital system packages such as dolphin and plasma-desktop. This is clearly a bug.... right?

Other packages like Krita presented no such behaviour, so I assume there's something seriously wrong with VLC, or what?

No it isn't a "bug" those are called "dependencies". You can remove VLC but will need to reinstall kde-plasma-desktop. More trouble than it is worth and you could completely break your system.

Okay, but I find that behaviour very odd. The fact that its so easy to completely break the OS just by wanting to uninstall a popular media player from discover can leave a bad taste in people's mouths and make them shy away from using Linux. But maybe that's just my opinion.

See: https://bugs.kde.org/show_bug.cgi?id=379721