That doesn't follow at all. One, it's established in DA:O that templars are chosen primarily for their religious fervor and loyalty to the Chantry. Two, supporting a standing army is incredibly costly. It's one thing for the Chantry to maintain a sizeable number of templars that's more or less comparable to the number of mages (or somewhat greater). It's another thing to have an actual military force.
Maintaining a standing army is expensive, but not that expensive. Medieval military orders, such as the Teutonic Order, the Knights Hospitaller, and the Knights Templar, were established, because there was a need for standing armies in the Holy Land and elsewhere. I somehow get the feeling that the Templar Order was meant to mirror those orders to some degree.
DA:O's codex - which is really the only time we get to read about templar abilities as they're seen in the lore, not gameplay - make it sound like they're very adept at countering most non-blood magic, which is why hedge mages and apostates have to resort to it to stay free.
They're good at countering magic targeted directly at them and disabling mages close to them. However, as any Ars Magica player knows, the proper way to fight enemies resistant to magic is to target the mundane environment and use it as a weapon. Templar abitilites don't help too much against burning houses, blocked doors, floods, and landslides.