Yeah I witnessed that aswell. This is what i found that works best to keep that from happeneing:
You have to create 5 decks.. lvl 1 cards deck, Lvl 3, lvl 6, lvl 9 and lastly lvl 10... You must not 1 hit kill the enemy... During elections before entering the bronze rank use lvl 1 cards, bronze can use lvl 3, I use lvl 3 until diamond, then diamond use lvl 6... I never use lvl 10 cards in arena though but I put it as my defense card.. I haven't try using lvl 10 in Master coz I'm tired repeating... Just to be safe don't use lvl 10 in arena.. "never ever 1 hit kill your enemy in arena"