I don’t know if you’ve solved this, but i had issues with translucent materials showing up sharp and in focus no matter what, and what solved it for me was going into the translucent material itself, and enabling the setting to output translucency velocity, or something like that, and then change the the order for processing DOF to “before”, instead of the default of “after”.
Sorry if I get some terms wrong; I’m not in front of the project at this time. Hope this helps!