Sure, as long as you have other options, I'd try the Steamer. I would still score the wallpaper w/the Paper Tiger because you want the steam to get under there. Personally, I've never encountered a situation where the DIF didn't work. As I mentioned, usually, the cause of the DIF not working is: not enough coatings, not waiting long enough, water not hot enough, mixture too 'dirty', wallpaper not scored enough or deep enough, wallpaper 'drying out' before it's pulled off. All this assuming that the DIF-to-Water ratio is being correctly mixed.
Again, if the wallpaper is vinyl, it's a harder job. Vinyl wallpaper needs MORE perforations than paper wallpaper. Be sure you're getting THROUGH the wallpaper w/the Tiger.
I someone is using a glue that's not meant for wallpaper, then there would be tell-tale signs. Wallpaper glue is not that 'powerful'. Other glues will 'crinkle' the paper, discolor the wallpaper when it dries, and be a HECK of a lot harder to work with when installing it even if the installer is a Pro. Obviously, I can't see what's going on. Try the Steamer or hire a Pro. Once you find out what's up, by all means, please let me know. (I'm sure I haven't seen everything ...)