I think the PT6 is a great engine. Anti-icing places a greaqt load on any engine.
It's a little unfare to say the PT6 is crap based on it's anti ice perfomance. Many engines have problems, and correct me if I'm wrong but the requirements have tightened up over the years. So a 70's aircraft may look to "out-perform" a 1990+ aircraft if compared simply on a "Anti/De-Ice on" perspective.
I know of someone flying a [an aircraft with a] PT6 for nearly 10 minutes with oil on their canopy and it still ticking along fine!