I have a simple flow that changes the owner on an opportunity to the account owner upon creation. It is called from process builder when the opportunity is created.  Three simple steps:
1. Lookup Opportunity (to get account id)
2. Lookup Account (to get owner)
3. Update Opportunity (with owner)

It works fine when adding opportunities from the UI or in small batches but any large load causes too many SOQL queries.  My opportunities are coming from another system so I have to be able to handle volume.  I have no loops in the flow and can't batch because it is triggered by process builder.
Any ideas would be appreciated.