RE: DIF - I've always used the NON-premixed solution. You know, the one that you mix yourself. I even go one step further and apply a 3rd coating just as I'm about to remove the paper so the paper is actually wet when I do so. It seemed that waiting 15 more minutes after the 2nd coating only allowed the paper and solution to dry. Consider trying a 3rd coating as you're about to remove the paper.
Also, are you sure the Paper Tiger is actually perforating the wallpaper? Obviously, if you press TOO hard, you'll have an awful lot of 'dents' in the drywall. You want to press hard but only hard enough so that the Tiger's teeth are perforating the paper. Take a close look at the wallpaper, itself, after you've removed it to be SURE that the teeth marks are actually through the wallpaper. (It's hard to tell how the teeth have done whilst the wallpaper is still on the wall ...)
As for bathroom wallpaper, this type is usually made of vinyl. This means that there is no 'paper' (per se) to 'absorbe' any of the solution. In a sense, you're relying more on the 'teeth holes' to allow the solution to get to the backside of the paper to 'attack' the glue. See what I mean??? There are times where I've made MORE than what I felt was the necessary teeth holes in the vinyl and the wallpaper STILL wouldn't come off! What I'd do is peel off whatever vinyl I could (carefully) peel off, and then do the 3-coatings-method I described earlier to get the remainder off of the wall. Just DON'T go pulling off the vinyl so roughly that you end up pulling off the top layer(s) of drywall too! Make sure it's just the vinyl/wallpaper you're pulling off.
In closing, as you're finding out, this job is a time consuming one. Make sure you lay some plastic sheeting on the floor, and then lay newspaper on top of that to absorbe whatever runs off of your wall. If your baseboard trim is still installed along the base of the wall, buy some Painter's Tape (NOT Masking Tape) and cover the top edge so you don't get all that 'gook' on your trim. And as you know probably, from what I've written in the past, be SURE to keep a boiling, hot pot of water on the stove (and don't burn the house down.) Use rubber gloves and one of those HUGE carwashing sponges too for soaking the wall with. Oh, I use a 3" Spackle Knife for the job. And when you THINK you're finished, wash the walls down with a clean solution BEFORE you Prime the wall for painting (or new wallpaper.) Sometimes, the DIF won't work if the mixture is too dirty or if the water isn't VERY hot or you didn't wait long enough (among the other things I've mentions about the Paper Tiger.)