I wonder, are you trying to have an arguement or get people angry.
Right from the wiki
"Templars are the ideal foils for mages, having been trained specifically to counter magic. Templars have the abilities to dispel magic and inhibit spellcasting, and they develop a considerable immunity to magic, primarily through ingesting Lyrium. Ironically, these abilities could be considered a form of magic in themselves[3]. Though their abilities are mostly used as a foil for mages and fade creatures, some of their talents can have practical uses for the mundane. Holy Smite for example, is an attack that causes magical Spirit damage. Abilities such as Silence and Lasting Cleanse can prevent even normal opponents from using their talents for a short time."
People usually get angry when they can't handle an argument.
First take a closer look at what you just posted yourself. Apparently a templar can stop rogues from hiding in the shadows, because 1) It's an ability and 2) Templars have silence, which disrupts abilities.
I'm having a lore argument here, not a gameplay one. k?
Second, there are no obsoletes. Yes templars train to counter magic, yes they have protection. Any protection has a threshold and a counter. A well trained mage can potentially brake through all templars defenses. It all depends on how trained/powerful is the templar and how trained/powerful the mage.