No. I would say that groups that do slide tests do them irregardless of who you are (unless you are a well-established pathologist who is changing jobs). Our group would not do slide tests. But our group would also not hire an unknown commodity. We have hired new fellowship graduates.
Checking references is one way, as well as checking with non-references who might know you. Poor skills include overconfidence as well as underconfidence. Overconfidence is a huge problem for some people - some pathologists are quite arrogant and do not recognize their own limitations or weaknesses. Thus, they can be equally confident of incorrect diagnoses as they are of correct diagnoses. This is difficult to assess unless you work directly with a person, and can also be difficult to assess before the person is signing out on their own. This is part of the reason, unfortunately, that some groups only want to hire people with experience. Groups have also been burned by people who make good residents but make poor practicing pathologists - sometimes this is related to work ethic, sometimes it is related to confidence, sometimes it is related to lack of knowledge in certain important areas.
Poor skills also include poor communication - either poor english or simply antisocial behavior. Arrogance fits into this at times (sensing a trend?). Inefficiency is also a problem at times - you need to get work done and not dawdle or vacillate over every single thing you see.
In a sense, the most dangerous pathologists (IMHO) are the arrogant ones. Lots of people agree with me. Big surprise, arrogant people tend to disagree with that statement and they see their confidence as a plus. But they are missing the fact that arrogance and confidence do not go hand in hand.