Ah dude, every class has it's own opness in vanilla. Warrior shines with support, that's how the class SHOULD work. U have a rage bar that fills when u get dmg, u get enrage when u get crit. As in your scenario of 10 people focusing a warrior, if he survives that, he SHOULD reck faces. If ur so salty about the synergy of 2 classes, u shouldn't however blame everything on 1 class. Also, if 10 people focus a warrior and he doesn't die, you're doing smthn wrong. With shamans and priests on horde side, u can purge the fuck out of him and srsly, if he just continues to blindly run after u, he will either get cc'ed or killed if u have some kind of pressure. Obviously gear will play a role. Blizzard gave each faction their respective counterpart, this has nothing to do with "omg pallies are so op we need to give them to horde 2". Shaman's windfury totem is also quite smthn, tho I'll admit pallies are somewhat better for supporting warriors and in general (especially in WS). As for 1 shotting, warriors aren't the only class that can global people, and while warriors have mostly dmg (yea u can support 2 but rogues/mages will be 500% better doing that), other classes have a lot more cc and utility.
As for your original post, basing u'r decision on what faction to choose solely on warrior + pally is op is kinda short-sighted.