The dawnbringer doesnt seem like much. It deals aoe damage and is in line or behind legendary troops. This is cool if it is used in pvp, explore, etc. However, it is not… it is being used by players who already have 1.5 million souls to burn, so that they can instant kill your entire team in arena.
And yes. 14 damage to everyone in the arena is a wipe, and its likely that their 10 damage, plus 2 for every yellow troop can get that high. Now add the barrier and its a complete loss. No matter how well a new player chose his troops, matched and played, he/she will take an arena loss and wont be able to advance.
Its really simple here. Lets not allow mythic weapons in the arena. Because in a few weeks, it will be a cesspool of Dawnbringer people with as many yellow troops as they could choose, just to troll anyone that wants to get souls. Im aware there is other ways to get souls, but why should that make it ok to ruin the arena?