1) Well, we are evil so let's take care of those champion of torm's...check.
2) Let's give assassins a form of hips that they should not otherwise have...check.
3) Let's make sure we got the best skills improved...+4 disp, hide, move silently, spot, listen, ect....check.
4) We have to strip all shifter's/druids from the real true seeing....check.
5) Those paladin's are to fast, let's remove their horse...check.
6) You know, those barbarians may still terrying rage use...no problem, we'll lower that to...check.
7) Let's nerf hips but not the assassins form since its different...in progress.
1. Clearly CoTs were overpowered... Before wipe I made a 5 Paladin/9 Monk/26 CoT that ate everyone for breakfast, and everyone and their grandma has made something similar. High AC, damage, AB, saves, monk speed, damage reduction... whats their weakness again? I guess the Abyss, but that's about it.
2. Assassins with HiPS? Perhaps you mean their ethereal ability? Its not overpowered... once a day for one round... big deal.
3. Skills on items are lower than they were before wipe. Xeg-Yi belt for instance used to be +8 discipline, and now its only +5 I think. All those epic rings given by DMs before wipe, like Epic Ring of Shadows, Epic Ring of Awareness, etc. have been removed from the module completely... not even DMs can have them.
4. Bioware True Seeing is way overpowered... its essentially an immunity, which we dislike here in NS4.
5. I think most players love the fact that horses are disabled (huge client-side freezes)... considering disabling them in the Abyss... perhaps someone would like to put up a poll or something?
6. Because a skill check vs. a saving throw makes sense...

Only CoTs stood a chance of making a save against, and even still the DC can easily be in the 50s, which most players will fail against.
7. Assassin's "HiPS" is already severely nerfed. See 2.