The "Sort by" tab doesn't have any options to sort by role, and if it's supposed to work with "Def.", it doesn't. Or "Group by" tab have only group or role sort, but doest have "By Group & Role" options. (Wotlk Classic and Retail, and dont work with MT OT sort as tanks in SoD)

Classic version don't support dungeon roles, so all related role sorting dont work very well.
A "By Group & Role" sort Option has no sense in the layout editor and sorting by role is not supported by the game, you can group by role, but not sort by role.
Simply use a group by "Role" and define 5 headers one header for each group, this is how the default "by group&role" layout works.