Noticed a few things with this skill. First of all, when you use a wand and you are in diggle form, you revert to your human form to use the wand. At least, if you are female, haven't tried it in male form yet. Second, you seem to loose the passive bonuses of some skills. I have noticed what looks like damage boosts from melee skills vanishing when I digglefied. Also, I have been unable to autodisarm traps in diggle form that I can autodisarm in human form. The difference in trap skill was only 1 rank's worth, since I had a 45% disarm chance in diggle form, and I was dealing with an acid bolt trap. I'm not sure if this second part qualifies as a bug or if it was intentional.
It was intentional. Your equipment applies, but not other skills, because you're a diggle, and not a human. In exchange your diggle form gets absolutely insane powers.
That would make sense, except the base disarm chance for an acid bolt trap is 35%. While I have a pair of thief gloves on, that only boosts trap skill by one rank, so I should have a 40% disarm chance. So I'm getting another 5% from somewhere. I'm guessing it's tinkering, except I have that on level 3, which should be enough to autodisarm with the gloves bonus.