Isn't the issue with that being that Kazra and Sul were part of different tribes (all of which have specific varying appearances in their own ways) and the Darkspear are the only ones who are affiliated with the Horde? While it makes some sense for Mag'har Orcs to be with Green Orcs in their respective starting zones it makes far less sense that starting as a Sand troll in the Darkspear starting area would happen.
Even the Dark Iron and Wildhammer Dwarves make sense to be starting in the Dwarf starting zone considering recent expansion events. Different troll sub races though? Not without some serious story changes to allow it.