The Thief issue has started to lead a life of it's own. All they are doing right now is repeating themselves to feed the flame.
Although I agree on some of the things they say, I think right now is not the time to complain. Most of us haven't even played the Thief.
To answer your question: there's nothing wrong with the Thief, atleast, nothing CB can't fix. Have some trust in ANet
About the Engineer: It's a new class, so it isn't that strange that it's being criticized.
All new concepts are criticized before they are accepted and embraced.