This is because
-Even if you go right up in the enemy's face, they don't even notice you. They should atleast go into alert mode if they hear footsteps and whatnot.
-It was to tempting. After running out of magicka after two attacks, I found it easier to just skip over the enemies.
-You can skip almost everything. After I got my first Invisibility spell, I would just skip everything to the quest objective. It was to tempting, magicka ran out to fast at endgame, and didn't regenerate fast enough.
I then realized, after beating the theives guild with it, that it was completely Over Powered.
I don't want to see it back the way it was in OB.
Chameleon I do want, but not only to about 60%.