You people keep suggesting new gimping techniques but you still fail to acknowledge the fact that we shouldnt have to do that. It should be the other way around. They got it backwards, hence, the game is broken. Broken. Broken. Broken. I limited myself to Assassin perk trees and that wasnt good enough. It is broken. Period.
I don't know what to say. I played the game without any "gimping techniques" (i.e, I just went ahead and played. I didn't constantly tell myself "ok, can't do this, I'll be too strong"), and on Adept difficulty, from level 10-48, I felt challenged. Nothing except pitifully weak things died "instantly", stuff could kill me, etc. So I've got no idea what to tell you. Your experience with the game does not resemble mine in the slightest.
But like I said in that weapon damage thread.... my first skill to 100 was only at level 48. And my highest damage weapon was around 105-110. At level 50. So clearly I'm playing a different game than you.

(edit: also, I stopped playing that character at 57. No need to try to push to 81. I'll try other skills on a new character.)
oh, and "limited myself to Assassin Perk trees" probably made you more powerful. Someone who has their perks less concentrated would likely have less overall power. Just a thought.