Hi Jon,
You make an excellent point about the impact of teammates with unhealthy self-identities. Besides low self-worth or megalomania, sometimes these types of individuals act the way they do because they are trying to mask the fact that they don't have the expertise or social skills needed to contribute to the team.
In the examples you gave, what strategies were used, or could have been used, to minimize the negative impact of these individuals on the rest of the team?