Now I understand why ppl call Cassiopeia broken

Oppressive is putting it mildly. She's horrifying in lane. She can spam her BS spells constantly, regaining mana with E, forcing you to cs under turret while she flings more BS at you. She never runs out of mana! Meanwhile chicks like cast two spells and have to B. Then once Cass gets 700 gold for Tear it's pretty much over - might as well just let her have tower while you farm Wolves or something.