In fact I found out that if I map the level of the rifts and do them all in order I lack no power nor level to finish the game.
The painless playthrough:
1 - Map the level of all rifts of a given map (or the whole game if you have previous saves to do so)
2 - Go on and close all the rifts and make all the camps in the map, go to the next map
3 - Do the story missions when you are in the middle of the level range (or when you feel like... really)
4 - Finish the game painlessly after closing all rifts and making all camps
Too bad I did it only for experimental purposes, I am unable to skip quests =(
I in fact did a full completionist playthrough (a stupid idea, I know, it is just the way I play RPGs and I had a blast doing so in all previous BW games) and will never replay the game again in any way.
But still, running around the zones and grinding rifts (closing them got awfully repetitive after the first few ones) and setting up camps shoud be completely optional too. Not something you have to choose if you want to get through the game as fast as possible. And I would not really call it painless either 