My guess is the early stages of planning for Legion caused some serious changes to Warlords of Draenor mid-way through its development. That the WoD team had to shoehorn in a bunch of stuff to bridge to the new xpac while maintaining their deadline to ship WoD. The Iron Horde and Warlords of Draenor just get pushed out of the picture so quickly. You have these set-ups for epic confrontations at the end of both of the faction starter zones that lead to nowhere. There's this huge build up in Frostfire Ridge and Shadowmoon Valley and then you're in Gorgrond, in the jungle. Fighting Botani, Ogres and Saberon. By the time you complete Talador, the Iron horde are basically defeated and broken with scattered pockets of resistance remaining in Spires and Nagrand as well as the apexis daily areas throughout the other zones. The Shattered Hand only control small parts of Spires, and the Warsong are mostly holed up in a couple of forts in Nagrand. Before the Iron Horde's collapse just sort of happens Gul'Dan and the Shadow Council are already taking center stage with that starter zone quest.
My favourite part of Talador is how Orgrim Doomhammer dies almost as quickly as he appears and you're supposed to care or something. He walks off of a ledge at the beginning of a nothing boss fight (into what, the water?) and then later appears in a cutscene only to die like a chump. At least Ga'nar had some sort of character arc.