How to Defeat Aria in Episode 4 Chapter 5.9 - Mana Overload - Waypoint With Adin
In this stage, Aria's damage, effectiveness, and effect resistance isn't high. So, it is not difficult. But if you aren't certain about clearing it succesfully, you can bring Roana, Elena, Shadow Knight Pyllis, Last Rider Krau, and the likes.
The most annoying things from Aria is counterattack and increase defense buffs. So, just land unbuffable buff on her before she uses her non attack skill. Or if you can't ( Cause of not being fast enough or others ), dispell that two buffs. By a non attack skill if you can for more survivability.
Though mana overload buff grant herself advantages, it isn't much. So, don't worry. Just watch out her counter, then defeat her as you usually do in defeating main story's bosses.