You can't say that, if I walk into a dark room holding a pistol I can't turn on the light by hitting the switch with either my free hand, or the pistol itself.
Taking away a use key might not even simplify. If what is being said is correct the weapon drops and a hand appears. This matches early (early) reports of using computer consoles with a mouse cursor. To me this just sounds like it's more complicated, not more simple.
As for ducking - even if it's useless in the game it feels right. Not being able to duck makes me feel very limited - makes me feel like the game just wasn't thought out well. Granted, forced ducking can be annoying, but many people have pointed out hiding in Deus Ex. Even better was finding new passageways and exploring in Deus Ex. Hidden passages aren't well hidden if they can fit a grown man standing.
And, finally, run keys are useless in games that don't have stealth. Both run and crouch are great for multiplayer (hide those footsteps), but it looks like D3 will be twitch multiplayer, so hiding isn't half as useful as speed.