As it stands, Invisible Blade only has two DC based abilities in those five levels. One is its signature ability, the bleed, and crippling throw. The bleed has a set dc of 35, whereas crippling throw has a dc of Character Level + 3 + Intelligence Modifier. Seeing as at 33 heal, you'll pretty much auto succeed on the bleed check, and those with no investment will just use Restoration, we could grant more focus to the existence and relevance of Int in an Invisible Blade's life.
Most I could see someone going for would be 18 int. With 18 int, and doing something like focusing on gearing int too, you could achieve a +10 to your dc with two fox's cunning for a whopping 45 if you did something crazy like gear int. This would require someone with 32 int due to the ever common low wisdom modifier to get a 13 or above on their roll, yeah, but it actually gives more interesting gameplay to I-Blade instead of being an auto clear.
If you did this by the way, your crippling throw would also be 43.