Well Euphie does have lack of good attack skills with force damage, so break through a green spirit/minion will be a bit annoying.
The reason why Narukana is so ...... powerfull/haxxed, is because she pretty much all in one character. Great in material and force damage. She has the highest balanced shield. She has a vanisher skill, a heal skill and damage support skill.
IMO in hard and super-hard mode she is a bit less powerfull than in normal mode and Euphie more usefull. *coughcough*
You should try play on hard and super-hard mode, some character/skills become more usefull and some less usefull. (be very very afraid/happy of skill with percentage damage).
Story-wise I think Ruputna's route is the worst. The ending is erm... quite silly.... Maybe it's just the air-headness that I dislike her.
Nozomi's route is quite plain. Nothing really special.
Naaya's route is bad. I'm neutral about it.
katima's route is nice.
Satsuki and Narukana's route are great. Although defeating the last boss is bit annoying (both have the same last boss).