ACL permissions not propagating to user group

We are a small all Mac creative agency running about 35 Mac Pros (2008-2014 models with 10.8.5-10.10) and a few Mac Minis. About half of them run Windows 7 and Windows 8 in Bootcamp on our network. The server room consists of a 2009 XServe running the old 10.6.8 version of Snow Leopard Server and 2 PromiseRAID fiber channel JBODS (not an XSAN config). A very simple user login setup consisting of a couple of workgroups (Workgroup and Execs), with "Workgroup" being the universal group for everyone. 97 user accounts total. All of them really only have File Sharing, and iChat enabled. The local Mac logins are universal and we all use the same login and password to keep it easy.

For as long as we can remember (years before I started), we've had permissions issues on our shared volumes. ACL will not always propagate all the time for newly created files or folders. When any of the shares gets down around 1.8TB or below we have major permissions issues but when above that threshold it comes and goes and isn't specific to any particular share. We've been using Terminal to "sudo chmod -R 777 /Volume..." to force Read/Write on affected folders and files that wind up with Read/Write, Read Only, Read Only and can't often be modified from a user's workstation. Have tried using Server Admin in place of Terminal for a while trying to properly adjust the ACL and POSIX member attributes to a Full Control or Read/Write setting plus selecting the "Propagate permissions" pulldown and applying this. It holds for a day or so and then newly added files wind up with the R/W, RO, RO info on them and some users can't delete the files while some can. At one point I thought that it was the Windows (Bootcamp) users that were causing conflicts with POSIX since they don't use the AFP protocol (and use SMB) but have seen plenty of Mac OS users up against the same situation. It seemed things calmed down a little until we got more than a few Macs running Yosemite now. None of those Macs seems to connect to our server via AFP anymore. They only connect (and revert over) to SMB. Apple threads seem to point to that being normal for Yosemite OS (favoring SMB protocol and ignoring AFP). I'm not sure if this is the point of failure however.

I thought I would bring this to the discussion boards to try and get some help. I've been hesitant to upgrade the server to a later version of Mac OS X Server because the newer versions are so streamlined that they lack all the settings that the pre-Lion versions have. I have prepped a migrated clone of the server using Mac OS X Server 3.2 with Mavericks and may light that up on our network if anyone out there can make a case for going this direction. Will these ACL issues be eliminated or reduced by going to a new version of OS X Server?

Thanks,

Mike