I'm not really looking for spoilers so I only took a quick glance, but it looks neat. I heard the main quest line wasn't that long so I've been avoiding it; however, if there are that many powers to unlock, it can't be too short. I'll probably resume those quests tonight.
They become semi-side quests once you reach a certain point in the main quest line. Technically, I think you only have to collect just one to three of them to finish the story. I'm not 100% sure though, I too have been too distracted by non-mainline quest thingies.
I just did my first one after about 50 hours and I really hope there's not many of them...... I didn't know what I was doing or if I was doing it right untill I passed it.