Siege weaponry has been used in Thedas for centuries, with primitive equipment used as far back as the Third Blight. Nevertheless, it occupies a peculiar niche in the tools of warfare due to its requirements. Any army wishing to produce trebuchets or catapults must be funded and organized well enough to procure both the necessary materials and the military experts to construct them. Throughout history, most armies who fulfilled such requirements did not take advantage of such situation. During the Third Blight, for example, Arlesans and Montsimmard constructed catapults to fling flaming debris at the darkspawn, but the expense of the weapons did not justify the limited damage they caused, and the darkspawn were ultimately driven back by the Grey Wardens, not siege weaponry.
Tevinter forces similarly had the resources to construct siege weapons when attacking the Free Marchers or defending themselves against the Exalted Marches of the Black Age. Instead, the Imperium focused primarily upon the power of its magisters, who were less powerful but more flexible than siege equipment, and who could more easily fall back when the tide of battle turned.
As a result, in the battles against the Qunari in the Steel Age, generals found to their chagrin that the great oxmen had left them behind. Qunari blackpowder is, most military experts agree, not magic—it is merely an advanced alchemy that makes their cannons more effective than any trebuchet could ever be.
Nevertheless, there remains hope. As centuries have passed since the last Blight, and mages are now safely held in the Circles where they harm none, the experts of Ferelden and Orlais may once again turn their great minds to learning. We need no magic, not where the minds of men survive unfettered. With our resources and commitment to knowledge, we can easily surpass the brutal Qunari on the field of battle.
The title of the source, Qun, Gurns and Steel: Military Conflict in a Post-Blight Thedas, is a reference to the Pulitzer Prize winning book by Jared Diamond called, Guns, Germs and Steel: The Fates of Human Societies.