Appropriately good suggestions. As it stands yah Terrifying Rage was removed to avoid giving players a fear like ability. But improving upon the skill seems interesting given parry and tumble grant extra AC as it is you consider each maxed out gives +5 with out buffs and gear, etc. And Taunting almost gives a -6 and enhance feature to counter that and the magical buffs and, gear, and enchanting Ac you get would be a counter to such higher uneasily obtainable Ac. Even so adding a diverse set of negatives would be cool considering the versatility of how Intimidating or Antagonizing your opponent could be beneficial in a fight.
For example:
Feat: Mocking
Requirements: 5 Persuasion, 10 Antagonize
Description: Insulting the opponent you demoralize them by making them fall prey to your insults. Whether it was a cynical intellectual insult or out right talking about their mother they seem more or less intimidated and enraged dropping their guard further against you. This applies a -2 Ab to your opponents attacks for the duration of your Taunt lowering their efficiency to battle you as you insult them on the go. Bard's receive this feat at level five given their cunning and bardic silver tongues as well as those Barbarians who uncivilized means of warfare are prone to insulting their opponents in battle.
Another example:
Feat: Distractive Offensives
Requirement: 5 Persuasion, 10 Antagonize, Mocking
Description: Taking further into your repertoire of devaluing behavior you now not only use words but shout and use obscene gestures to distract your opponent. While this provides an attack of opportunity against you if successful further demoralizes your opponent drawing away their attentions to you. This causes the opponent to suffer an increase spell failure +10% from the 20% from Antagonizing, further with Mocking included when you perform this action you draw the attention of all hostile enemies to you when those that fail the Discipline Check vs Antagonize.
Yet another Example:
Feat: Intimidating Presence
Requirements: 20 Antagonize, (Starter feat that encourages intimidation), Mocking, Distractive Offenses
Description: Having been a demoralizing, unsavory, and rude individual most your life you really don't care who or what opposes you. Just the fact they even think they can oppose you boils your blood making you meaner and angrier than usual but woe to the fool who stands against you. You suffer a -2 to Will Saves for your impudent rage but your opponent is so beguiled by your intimidating presence when afflicted by it they suffer a -2 to Parry/Discipline/Tumble against you unnerved beyond belief. If this is used upon an opponent Near Death, similar to Warding Gesture, the opponent makes Make a Will Save DC: 1/2 Player Level + 1/2 Antagonize and the individual fees from combat as if routed.
I hope these suggestions help and offer some insight. Hope I don't offend anyone or aggro anyone on these examples they are just examples after all.