The legions only cooperate because there are the ghosts and the flame legion to keep them occupied, otherwise they would fight amongst themselves (well.. they do against the flame). They like other legions as much as they like other races.
One can say charr would unite against the asura, but theres no evidence to back that up. more easily one charr legion would try and wage war on the little muppets on their own, like flame did against humans, overpowering the other legions (not sure on this).
Im getting tired of repeating ,myself. Asura have shown before (GW1) union and cohesive military action against the destroyers. that included battle golems (at least 3 of them) with 3 battle modes, on the gameplay plot, where the dwarven stone army consisted of 5 or 6 dwarves. so scale it up
The golems back them had, at least, 3 battle modes: Melee ranged and healing, showing how adaptable the golems are. There were dungeons (oolas lab) where you would encounter many more golems, with magical powers and even indestructible (almost) ones. Also asura had magical devides to call golem airdrops. Asura tech was crucial to defeat the mursaat (war on kryta plot). All this while probably still fighting in the depths against an elder dragon.
Dont forget who defeated the united charr legions: the mursaat and humans..
Edit: after reading seems like my text indicate to contradiction, it doesnt: Flame legion fought the humans on ascalon. united charr fought the humans in the events preceding the cataclysm in orr.
Edited by The_Blades, 08 February 2013 - 11:34 AM.