Hi Vladislav,
First a fall would like to know, are you getting error from BI-LaunchPad or from WebI Rich Client tool.
BI-LaunchPad looks from 64Bit Oracle Native client (Administration installation) which should be present on the server side.
The machine on which IDT works fine, WebI RIch client tool should also show you the output.
On Windows server 2012, check whether SQL-PLUS 64 bit is getting logged in fine for the respective service or not. If it gives same problem means tnsname.ora file is not configured properly.
Take your Oracle DBA to get it configured.
Once SQL-PLUS 64 bit will started working fine, check the behavior from BI-LaunchPad.
Also BI4.0 also works without setting Oracle_Home, the default entries of Path environment variable is sufficient.
Hope this will help.
-Abhi