(The post is based on own experiences and learn from others who manage and build UX teams. Comments are more than welcome.)
Building an effective UX team primarily depends on your vision and personalities that you would like to inculcate within your team to deliver business goals. Many factors effect this, and some of them are the size of an organization, existing structure of the design team and UX maturity within an organization. Non the less a UX team needs diversity and helps deliver any problems that come their way.