Unfortunately, I don't have the opportunity to be paid to write Haskell. Which means I haven't had the opportunity to use it for anything else than side projects.
However, there is one thing you want a debugger for in Haskell: checking when thunks have been forced.
Also, the type system can catch much more issues than "normal" compiled languages, not to mention the safety of immutable values. But there still numerous classes of issues which will not be caught by the type system. And of course, you have exceptions. Even if your code catches them, figuring out what triggered the exception can be tricky.
However, there is one thing you want a debugger for in Haskell: checking when thunks have been forced.
Also, the type system can catch much more issues than "normal" compiled languages, not to mention the safety of immutable values. But there still numerous classes of issues which will not be caught by the type system. And of course, you have exceptions. Even if your code catches them, figuring out what triggered the exception can be tricky.