Using vray and deadline here i can tell you that it does work to distribute one image to several machines and in that way get more cores rendering one image.
However, its not like the regular distributed checkbox that is in the vray rendersettings, for that you dont need deadline. When submitting a frame throu deadline you can choose to split it up to several machines, then assemble that frame after the redering is done, There are pros and cons with this. If your renderoutput is multichanel exrs then the passes will not be assembled and that needs to be done manually wich can be a pain in the ass.
Why not just use the distributed option in vray settings?
What you need to do is to add the hostnames or ipadresses of the slaves that have vray installed and then enable them.
Sometimes it stops working for no apparent reason, i havent found a fix for it yet, On different projects different slaves gives up and wont be working eve thou we reboot them. Just getting the error message that the computer actively denied the connection even thou firewall and antivirus is off on those machines. Next project they might work fine again, and its always different slaves.
Hope this helps you.