...

I have 8 zserver threads and a ZODB pool size of 10. I'm fairly certain I'm not maxing these out. So is this blocking effect just expected behavior for zope?

No, there should be no blocking.

Although some colleagues reported similar behaviour with a (non Zope/ZServer) multithreaded application connecting to Oracle.

They could not yet find the cause of their problem...

Interesting. Are you aware if your colleagues' was a python(/dcoracle2) app? thx Jim