I think Fortifius should be an aoe spell because It could maybe scale up of the duration depending on what skill tree point a person has on it there, Plus The Defensive Spell tree mostly focuses on Healing, Supporting, and Curing Status so why not make Fortifius an aoe or casting it on someone like volo does depending on how close to a certain person or in yalms of how close you are between your friends/teammates In battle against opponents and mobs.