Defaultroutine works well for midranged decks. You need to construct a deck worthy of the bot playing for a starters. I've had 8+ wins before, never 12.
The problem with asking for an 'average' is that you're now excusing the fact that sometimes you just end up with a really shit deck. And that can happen more often than you want. Meanwhile your opponents get 2 legendaries. Arena is a gamble at the best of times.
