I really have to disagree with you there, Cellia is a safer duelist, with heals unless Conrad is getting oneshot he's gonna be better. 279 defence is low and is not going to make or break things. The MR and higher health is gonna be useful in some places but an extra 639 attack is far more useful than an extra 37 defence for Cellia.
Often enough in events you'll have to put a duelist down with no support other than some occasional healing with skills, in these situations Cellia will take more damage than Conrad. There are also places where things need to die in time before the next wave comes where Cellia will do badly.