Tested the new feats for a charismatic fighter and came across a minor detail that may not even be a bug.
When singing "Rallying Cry" or "Inspire Competence", there's a visual effect on allies who are affected by the feat, such as shown on the guards in this picture:
But when it came to "Last Stand", the effect simply doesn't triggers on the allies, except the character singing the feat (as it says in the log chat).
Also the "singing" of the feat appears for Last Stand, but doesn't for Rallying Cry, as shown in the pictures.