What constitutes the best balance depends on the department. Balance is also going to depend on whether we consider ourselves a primarily teaching or research institution. Balance will change depending on the emphasis. Load should include number of students, grading, accreditation, internships, course, development, adjustments for junior faculty, multiple preparations. Load should be 5 courses, not 6.
Flexibility is key.
Increased load would hurt connections to students, neighborhood, community, discipline. Maintain a commitment to have classes taught by FT faculty, not move to the TA format. Class size matters for load. Avoid ghettoization of teaching, with a split Teaching vs. Research Faculty. One student who spoke pointedly about the value of his undergraduate research experience prefaced his comments with an affirmation of the priority of excellence in teaching.