How is it tough to get those numbers in a fight? As you fight a boss cast water spells on it.
Manipulating an enemies AI is the foundation of most game play. You study an opponent and counter it. Boxing a mob in so it can't hurt you is different than setting up situations so the boss acts in ways you've anticipated. A Feca's proposed Belligerence skill does exactly this. It makes the boss believe the Feca is weaker than it is. This will cause the AI to do things it normally wouldn't. Instead of ignoring the very tough Feca it will attack hoping for easy dmg.
As to the resistance debuff, i agree it's a valuable resource when it stacks enough levels. But again, those numbers sound good in theory, and are really hard to achieve in the actual game due to multiple variants. I insist pandawas need more options when it comes to provide utility to their team.
And if that's what you meant by "manipulating AI" that's ok, I thought you actually meant using exploits against the enemies xD