Regarding lack of difficulty - didn't I read somewhere that on the hardest level you're dead if shot at for more than 1 second? Sounds challenging to me ;-p
No, its not. Because on Deus Ex if you chose 'Realistic' you could be killed in a single headshot from things like Pistols, a single shot to the torso or head from a Sniper Rifle was instakill. Automatic weapons and shotgun weapons would cause serious damage (but weren't accurate enough on enemies to kill you immediately except at close range). All of this time you had to manage Medkits to heal up those wounds (and you could spec to make them better) and later on you got a Regeneration augmentation (which was a little unbalanced at max rank) which meant you had to manage Bio Energy too.
Regenerating health on Deus Ex is retarded. The game is clearly designed for morons who need to feel good about themselves even if they fail. If you take lots of damage while stealthing, you were crap at it, if you took lots while shooting everyone, you need better weapon skills or to not suck as much.