So wait, at what point did the Seekers emerge as a separate organization from the Inquisition?
From what Ameridan implies, the Seekers were originally a division of the Inquisition, who took on the role of Internal Affairs after it was disbanded.
His memories showing that one of his companions was all for taking Lyrium to fight demons, implies that the Templars rose from those in the Inquisition who wanted to have similar powers to the Seekers, without undergoing through the arduous training and semi-possession ritual, that according to Cassandra doesn't always work even after all that?
We learned in DA2 that Templars have a night of fasting and religious contemplation before taking vows and lyrium for the first time, which when you compare to how Cassandra mentions doing a similar fast and prayer for an entire year, seems like the ritual was probably taken from the Seekers but scaled down?
All in all, it makes Templars seem like they were formed from those who wanted to fast-track becoming a Seeker and took shortcuts to get there? And with how the Rite of Tranquility was later abused and forced on mages, one can't say that Templars aren't fond of taking the easy options?