I haven't used Fiverr but I have recruited on craiglist and in-person for what I would call a 'social media editor' and never wound up happy with the work I was getting and what I was paying for it.

In my mind a writer like that has to write "a lot" of articles (e.g. a lot of words total, but not many per articles) and be expected to reach a certain levels of quality, but not to do the amount of work that somebody might put into some things. I felt like I could reach that standard myself but couldn't really get others to go there -- some people had no standard for quality at all, others wanted an hourly rate I couldn't afford for what they produced and thought my piecework rate was too low. Maybe half of it was intrinsic to the situation, maybe half of it was my not being good at hiring/managing and not trying for longer.