When you say...
"Anyway - dont use Workstation for any VMDK-operations on ESXi."
..., do you mean that it is not a good idea to copy VMs created by Workstation onto the ESXi server and use them, or are you referring to conversion type actions? The VMs I have uploaded to the ESXi server via drag and drop after connecting to the server in Workstation seem to be working OK (though they may not be streamlined or efficient).
I really think my IT department should be handling this, but I guess they don't have a problem with me struggling with this.