Jaheira was introduced in the game for fanservice
Except reducing legendary epic characters into mid level companions is not fan service.
Minsc and Jaheira riding in as NPC's to save the new party's ass when things look hopeless would have been fan service. Them taking out someone like Kith'rak Voss and his Red Dragon in an epic cutscene would have been fan service. Minsc knocking out the most badass Githyanki in a duel and Jaheira striking the dragon down with lightning, binding it with roots and Minsc coming back to cut it's head off.
That would have been fan service. And a good way to establish some power structure in the game world, showing that the PC's are not on the top yet.
But Larian doesn't get that. They have an uncontrollable urge to present low level PC's as equally badass. That means not Archdruid Halsin, not Minsc, or Jaheira get to be more badass than the player. Maybe Elminster could also be a 7th level Wizard companion.