A helpful overview from JDSupra that notes how the court addressed common class certification disputes issues is available here (excerpt below):

Although some of the plaintiffs could not accurately account for the exact amount of time spent performing non-exempt tasks, the court noted that “courts in overtime exemption cases must proceed through an analysis of the employer’s realistic expectations and classification of tasks rather than asking the employee to identify in retrospect whether, at a particular time, he or she was engaged in an exempt or nonexempt tasks.”  It stated that “[b]y refocusing its analysis on the policies and practices of the employer and the effect those policies and practices have on the putative class, as well as narrowing the class if appropriate, the trial court may in fact find class analysis a more efficient and effective means of resolving plaintiffs’ overtime claims.” ( link)