Yes. It's best to wait until you've completed at least the second chapter of the story and sufficiently leveled your phantoms. Then at least, you can try and take out the enemy fast and furious. My strategy is to throw all enemies Out of Bounds. This will work until there is one left and that one will have been leveled up each time you OB'd an enemy. That's a lot of experience to deal with only one enemy with all your best characters. As long as Marona isn't killed, she can start every battle by OB'ing the enemies until only one remains. Remember to save after every accomplishment, even if that is something as trivial as buying a seemingly cool weapon from a Merchant (another phantom you can create).