When I see a team recruiting, especially for level 50 content, I ask the recruiter if they need anything specific. I can supply anything except dedicated healer. Otherwise I go with what works best for what they're running; debuffs for Kahn, tank with CC for BAF, DPS for Lambda, ice/plants blastroller for Hami. and so forth. Eventually I settle on one or two characters for those roles, and those characters eventually become T4 incarnates. They still get played to supply raw materials for the Factory.