Mass tort action lawsuits are quite different from class action lawsuits. In a mass tort lawsuit each plaintiff has an individual claim resulting from distinct damages and therefore each plaintiff ultimately receives their separate trial.
However, in a class action the many plaintiffs typically are not considered individually and there is only one trial and/or one settlement in which most (if not all) of the many plaintiffs equally share in the settlement amount.
There is no real individualized determination of how the harm complained of specifically and actually affected any one individual plaintiff.
This is one of the primary reasons that pharmaceutical mass tort lawsuits are not routinely pursued as class action lawsuits.