@syric89
Spearwall (just like almost all actions) is not guaranteed to work. The Orc (or Orcs) got lucky.
We are after all dealing in percentages. If you have 80% chance to hit, then you also have 20% chance to miss. Not to sound patronising, but you do have a chance to miss, and you could have just been very unlucky.
Perhaps it needs testing to check that its not a bug? But like I said, you could have just had very, very bad luck; it happens.