I've heard if you ace all 3 rolls, the Netherbrain has around 20% less hps.
I've passed the first 2 checks, but not enough inspiration left to pass the last one. With 4 inspiration and Enhanced ability, you have a 40% chance to beat DC99.
On higher difficulties it's 10% less HP. Also, to ace all 3 skill checks it is highly recommended to scumsave DURING the cutscene.

Also, if you ace all 3 more info is revealed about the brain (and the cutscene is cool as heck, so yeah, I scumsaved away until I hit nat 20 on my 1st run).