As with anything in comics, keeping things the same just makes everything predictable and stagnant.
so i'm enjoying the paces DC is currently putting their heroes thru in regards to questions like this.
Personally I don't think it tarnishes the heroes one bit if they make the odd exception every once in a blue moon depending on the circumstances. Jus so long as you don't go all "Punisher" on Batman or Wonder Woman to where it's a primary or expected part of their character.
A death should shock the reader but it should also be a logical conclusion of a particular circumstance. Simple death for it's own sake is never good nor very heroic.
As for the Joker, i'm more concerned as to why he's still wearing that stupid old fashioned tuxedo rather than whether he's been allowed to live too long or not.
Everything is funny as long as it is happening to somebody else. --Will Rogers
"I don't think anyone anticipated the breach of the levees." - George W. Bush
I don't think anybody could have predicted that these people would .. try to use an airplane as a missile, a hijacked airplane as a missile. - Condoleeza Rice
Barbara Bush: It's Good Enough for the Poor
To comfort the powerless and make the powerful uncomfortable.