No he got praise for it because he was good in it and the Dark Knight was a good movie.
He was good in Brokeback Mountain as well. He was also good in Candy. From what I can see from those movies, he had some talent.
Similar things happened after River Phoenix died, further back James Dean would be the obvious one. Both of them were great actors too Had they not died they would have become even better.
After Brandon Lee died tragically on the set of The Crow there was a massive outpouring of grief, and also lot of tasteless spooky talk about the "Lee Curse" . However I think what was most sad about him is that he never really got the chance to show his full potential, even though The Crow was entertaining enough. I feel he would have probably gone on to something even better
Maybe we would have seen him cast as Neo in the Matrix and become a massive action star. Maybe he would have worked with Jet Li
We'll never know, and that's my point. He never got the chance even though people remember him with fondness and still love The Crow.
At least Heath Ledger succeeded in showing the world what he could do while he was still alive. He was pretty damn near to being at the top of his game.