I had a similar situation. I built my own house so I guess I was the dumbass builder. I knew not to put wallpaper on bare drywall, but I thought a coat of primer would suffice. Wrong!
When I tried to remove the paper about 10 years later, it was impossible to take off the wallpaper without gouging the drywall paper. I tried the paper tiger and at least 3 different stripper products.
paper tiger
http://www.acehardwareoutlet.com/(g4ohzpzkz25evs551nrxpj55)/productDetails.aspx?SKU=998009052
I eventually had to skim coat the entire wall. I really suck at drywall skills so I eventually hired someone to finish the job at a reasonable price.
I did not rent a steamer. Not sure if that would have worked, but the quote from the guy to finish the job was so good I didn't pursue it.
If I ever do wallpaper again, I will be sure to use wallpaper sizing first.