It is not, NOT, really possible to get out of Arena Bronze I (perhaps II). Arena is still messed up, as it is since months. Look at the Missions: I am at "Reach Silver I in Classic Arena" - which is absolutely not possible with all the Legendaries at Bronze I (Average team power at about 80-120 I would guess). THE NEXT mission would be "Clear Stage 7 of the Catacombs of Narbuk on Hard" ... I'm done with the Campaign on Hard completely or the next "Clear Stage 5 or higher of the Minotaur's Labyrinth 10 times in Auto". My teams does 10 times in Auto at stage 15". The difficulty of the missions should be comparable! But no: no fixing of the Arena bug since months!!! So it's not you, it's Plarium.