How drastically would the villain change? I believe he would be much more dangerous, as he wouldn't have his lack of sanity block him from achieving the goal he should be trying to go for; killing Batman and becoming a successful crime lord. After all, The Joker would be much more successful with what he does without Batman interfering and he is the person who made him what he is (even if it wasn't on purpose).

What do you guys think?

I think his chaoticness is what makes him so dangerous, if he became sane he would just be another Black Mask or something. And even more boring then he is now.

Better - what if he is sane all the time?

Trick question, as the Joker has always been sane.

That's what everyone thought in The Dark Knight Returns but he ended up murdering the hosts of a talk show on public television to get Batman's attention.

I think he became sane in the first place during TDKR is because he probably thought Batman was dead. He's said a lot of times that if Batman died or stopped being Batman, Joker would stop doing the nasty shit he does. So it's very likely that Joker in TDKR was never really sane to begin with, he was just relaxed and bored.

Already happened.

@symbioticspider-man: many people think that he is sane and just uses it as an excuse

Some think he has super-sanity (look it up)

-hood