Every set in Hearthstone has its fair share of surprise cards. It's easy to misjudge them when you can't actually test them out for yourself let alone without knowing what the rest of the set contains. It happened with Dr. Boom, it happened with Mysterious Challenger, and now to a lesser extent, it's happening with Dirty Rat.
What Pros Were Saying
The closest equivalent to Dirty Rat is Deathlord so many were immediately saying it would be a suboptimal anti-aggro card. Brain Kibler described it as "one of the most interesting neutral cards" in the expansion but was "skeptical" about how excited the community was when it first released. Many believed it to be a replacement that would still be somewhat useful in today's more aggressive meta where small minions continue to flood the board. Maybe this could trade into one or two of them and somehow slow their roll.
What It Ended Up Being
Instead, Dirty Rat has become a control card to draw out your opponent's minions before somehow clearing the board. It's particularly good against other control decks where you can really get incredible value out of it. Check out some of the clips below.
The lesson of the day: it's hard to rate cards. This one is good for sure.