"occur" vs "occurs" with a singular collective noun

You are correct. It should be occurs because you are talking about a batch. Now, a batch of what? That is something else.

The confusion can be eliminated by removing what the collection is about. Like, the list of guests is lying on the table. Some may like to use 'are' here. So let's forget for a moment what that list is about and rephrase our sentence- the list is lying on the table. I hope there is no confusion now.

Similarly, a group stands at the gate and waits for the president to come. Or, a group of men stands at the gate and waits for the president to come.

One thing cannot occur together, unless it occurs together with something else. Thus, it has to be "a batch of writes occur together". See Google Ngram.

There are a lot of collective nouns (like "a lot") which can take plural verbs in English. See, for example, this question.