True story.
A contact of mine hired someone to write their blog and social media, and asked me to take a look.
Blatant truth: it would have been funny if it wasn't so sad!
The content was very flat and devoid of emotion, while my contact is a highly enthusiastic and emotional individual. The content sounded nothing like them and, in fact, didn't represent them well, at all.
Here's how to best avoid this situation:
Review your prospective resource's portfolio to determine if you like their "style" and if it is sync with how you sound.
Interview them, and discuss your goals, and how you wish to come across on the various platforms. Get their feedback.
Ask them to write something for you. Expect that you will pay for this "customized" sample, but trust me, it is well worth it to see if they can be true to your brand.
If you aren't happy, go elsewhere and interview more resources. Never settle. There are options galore and you should be happy with what the writer is producing for you.
Don't accept anything less.