My PW is Wrenn an Six. With Fangblade Brigand on the board and using my PWs second ability (dealing 3 damage to any target - in this case targeting the other PW), Fangblade Brigand doesn’t get +1/+0 and first strike.
But since it is non-combat damage, it should get it, right?
Hello @Fliggl,
Thank you for all the information provided, this issue will be investigated!
If you have any additional information that you consider relevant, please don’t hesitate to send me 
Rebeca.
I tried it again and included Flame Channeler in this deck, too. Non of the two creatures were triggered by Wrenn and Six second ability. Nor when I activated the transformed Arlinn Kords (EDIT: the vanguard) second ability (deal 3 damage, transform this card).
Valakut, the Molten Pinnacle on the other hand, triggered their abilities
This issue should now be fixed on the current live build.