From the front page
So if you keep all of your progress when you switch, it doesn't sound that bad. It just sounds like it's designed to be something you're not supposed to switch for every fight, because you can't just go and do a small number of tasks mid-raid to switch your covenant.Swapping into another Covenant will not be hard, but rejoining one that you left may require additional tasks to be completed. Once you do, however, you will keep the progress that you made in that covenant prior to leaving, including all of your renown and soulbinds.
But if you keep your progress, I could even see myself going through all of the covenants on my main character, to see the stories. If switching isn't going to be punished by reseting your progress, that's like the most important thing.