It's not.
They could have united Warriors by making a Class Hall that serves as HQ for everyone but has race-specific quarters by organizing the Warriors in regiments. That would fit the military Warrior fantasy perfectly without shoehorning them into this Valhalle theme. Because it's wiser to emphasize everyone's strengths and combine them.
That means, we could have something like a huge fuckin Fortress with a
neutral Main Hall in the centre where the Generals meet to discuss tactics and strategy while the standard soldier is sparring, drilling and working in their respective, race-specific quarters/barracks.
Orcs and Humans provide the main battle force and backbone of the army.
Dwarves are responsible for the Smithy and Armory.
Gnomes and Goblins tinker new war machines.
Night Elves lead the vanguard and scouting parties.
Blood Elves bolster the defenses against magical enemies.
Worgens are very mobile infantry, practically light cavalry.
Taurens serve as shock troops or meat walls.
Draenei function as field medics and tend the wounded when no real healer is available.
Pandaren maintain logistics and supplies for the war effort.
Trolls...keep the morale up
That saying: it's not like that a Draenei exclusively serves as field medic or a Dwarf sits in the Armory all day. It only represents the main responsibilities,strenghts and stereotypes of each race. An exquisite Troll Smith will of course help crafting more weapons and armor, a stout Dwarf will stand beside a Tauren to hold a critical chokepoint with shield in hand. In the end, all work together for a common goal and most of the Warriors are used at the front lines anyway.
We, their Commander, would lead them and make best use of our
combined forces.
At least, that's what I imagine when I think of Warriors preparing and going into war.