I disagree about not starting with a offensive type soul. I've said it before but Nike is more than get you through current level content, Andromeda is just overkill as it stands. I would only bother to get her if you really want a full element party and don't have a healer of your current element. Going Arthur would be easiest as she has the best all-round damage and killing enemies is by far safer than trying to play defensive and heal. No need to worry about overdrive meters and healing when the enemy is already dead.

"Oh but what about raid bosses?"

They're irrelevant since you don't need to solo them and by the time you can solo them, you should already have enough Soul P for 2 or 3 Legendaries.