I just wanted to put an official response here for people that search in the future. There was a question about whether or not you could use Erkenbrand's ability with damage cancellation like Honour Guard or Raven-Winged Helm. Here is the official answer:

Hi Jim,
When a player uses a Response to cancel an effect, the result is that the canceled effect never resolves. For example, when a player uses A Test of Will to cancel the ‘when revealed’ effects of The Necromancer’s Reach, the players do not deal 1 damage to each character in play and then remove 1 damage from each character in play. Instead, no damage is dealt.
Similarly, if you use the Response effect on Raven-winged Helm to cancel the damage just dealt to Erkenbrand after triggering his Response effect, you do not place 1 damage on Erkenbrand and then remove it. Instead, the damage is not dealt at all. In which case, his cost has not been paid and you cannot resolve his effect.
Visually, it looks like this:
Damage is dealt by effect ——> Response effect cancels damage dealt ——> No damage is actually dealt
Cheers,
Caleb

I'm a little confused. With the combo Gloin-SongMocking-Treebeard seems it runs:

https://community.fantasyflightgames.com/topic/180443-treebeard-hero-song-of-mocking/?p=1664548

There were a few different things in that thread. The one that relates to this thread is that if you use Treebeard's ability but he doesn't actually take the damage, he does not get the bonus. You can still trigger his ability to cause the damage, but since you didn't pay the cost you don't get the benefit. In that thread they were just trying to deal damage to Gloin on command without actually gaining a benefit on Treebeard.

You could theoretically do the same thing with Erkenbrand and Gloin, although it's not nearly as useful. Reveal shadow card -> trigger Erkenbrand's response -> Redirect damage to Gloin -> Erkenbrand's response fails because the cost was not paid.

Notice the answer was very precise and he said the damage doesn't RESOLVE. That means the damage still activates (for lack of a better word) but doesn't resolve. That's why you can still only activate Treebeard's ability 5 times, even if it never resolves once.