Getting a lot of 404 links to resources that have never existed on the page. Should I be concerned?

Could be a bandwidth exhaustion attack from bots, trying to use up all the available bandwidth for the client, by sending repeated requests, or they are just trying blind attacks against specific themes’s known vulnerabilities which usually are hosted at those uris ( like/career or /event).

If its an important site, and this traffic grows, they might want to explore more secure hosters/options