So, for the Radiant's progression in the oaths, I would guess that their speed is pretty normal. The Skybreakers expected Radiants to progress much more slowly than the likes of Kaladin, Jasnah, and a lot of bridge 4, but that was pre-desolation. Constant combat puts a lot of stress on people, which is why we see a lot of Radiants leveling up during battles. As for the power levels of Radiants, my personal theory is that Windrunners are drawing some of Honor's splintered power to themselves because of their high levels of connection to that shard, both through their bond to Honorspren, and their personal convictions. That is why they were the closest to waking up, and why Kaladin stayed awake when none of the other Radiants did.