Oracle OIC integration pods integrations grouping criteria - Best Practices

Summary:

I would like to know if anyone has a followed a defined criteria in your organization in placing the different integrations across multiple OIC pods?

Content (required):

For instance, let's say we have 3 OIC pods(instances) for each environment (Dev, UAT, Prod i.e 3*3 = 9 total OIC instances) and in our case, we see the pods are pretty unbalanced. One of the OIC instance pod is heavily used with most of the scheduled integrations resulting in scheduler issues. We are working to spread the integrations across other pods and has anyone in the followed a defined criteria or grouping which has worked well? Like placing financial, HCM, Procurement integrations in 3 different pods (just a thought). Any best practices which have worked out well is most