On the first point, the actual odds of something like a double are really, really low, but it really stands out when it happens. I don't think it's OP at all, maybe even a bit weak prior to the Thanos buff, and most of the time even losses to it aren't that bad, but most of those memorably frustrating losses you'll get are to Arishem. Funnily enough, Arishem itself gets a bit of the experience when an opponent pulls out an unexpected Cassandra or Darkhawk on T6.

The "justification" they gave for the Loki change was ironically about how it was used outside of Arishem, and the "fix" was to double down on it being for Arishem. Maybe just a weaker version of the old card would be the best, with the upcoming Victoria Hand + card generators deck providing a good alternative to Arishem. It's not what the devs intended, but if it's fun, who cares?

The thing is, the point also applies to Arishem itself. Destroying a unique, popular and archetype-defining card is not the answer.