In my experience, devs make terrible QAs, since they know what the code should do and never think of things like "pasting a novel into a textfield" and the like

In my experience, devs make terrible QAs, since they know what the code should do and never think of things like "pasting a novel into a textfield" and the like. They also tend to be much more expensive as well. Combine the two, and it's just not at all an efficient use of a company's budget.