Interesting suggestion, Ken14.
It seems a well-intentioned post but there's a couple of wide-reaching implications if this were to be implemented that I'm not sure you considered when writing it. But don't worry, it's hard to keep in mind everything and it's why it's not at all enviable to be a developer because power creep is a genuine worry to consider when implementing abilities. Personally I'd like to see it implemented as someone that plays a melee character that invested in antagonize but it'd be extremely unfair to anyone I fight in both PvE and PvP.
Addressing the first question...
So I wondered: why isn't there any feats surrounding this ability to improve the sheer otency of how it rattles people?
Permit me to be a bit pedantic but there is two feats that help facilitate the use of antagonizing mobs: There is a Half-Orc specific ability
here and you could argue that
skill focus is also another feat that plays off of this purpose but I suspect that you already know about skill focuses at the very least. I suspect that there isn't any additional feats on top of that because itemization already provides an inherent problem for spellcasters because there's a multitude of items that provide sizable antagonize increase with minor debuffs (source: Ring of the Mouth/
Revolutionary's Sash) and if we were to bring this theoretical fight to a higher level scheme enchanted equipment already provides
+6 and +3 antagonize with certain popular linings that I'll keep FOIC out of respect of what the server is trying to cultivate.
Unfortunately for any spellcasters, they're in an inverse situation with absolutely no concentration gear that isn't above a +2 concentration and certainly no crafted gear to help them out. On top of that, skill focus is their only feat and it's a CON-based ability so at
most inherently they have +3 or +4 bonus from their ability with +1 or +2 more from bear's endurance. Now also bear in mind that everything is equal footing for the attacker and the defender because they're still endowed with the bog-standard 23 points they get from 20 levels but things could also fluctuate because the focus isn't always on high-level play here. So already, we're looking at a lopsided bonus for one side over the other.
Which ties into the second point...
Like, for example, an ability that you can use several times per day that can do a deficit of up to 10 AC, and perhaps an increased spell failure chance of 100% for 6 rounds? At the cost of needing to overcome an increased DC?
A round is six seconds so six rounds would be thirty seconds which already makes me all hot and bothered here. Why? Because I invested the points and stripping 10 AC is essentially invaldied improved expertise for the cost of one feat or if it's a free class ability, even better, as opposed to their two invested feats which is a fairly big feat investment for some builds like bard. Against melees, it's promised to work until people start to feel obligated to invest
another skill, concentrate, in a manner akin to how we treat discipline currently which would ruffle some feathers because the big three (tumble, discipline, spellcraft) would become the big four and it could very well consume some builds whole and leave them dry on skill points which further makes fighters even more one-dimensional. That doesn't mean they're bad but we are kicking that class a little more if we implemented it.
But what against spellcasters? With this implemented, I would triple down on my skill and start getting all the antagonize gear to overrun the wizard's fully invest concentration (and not all wizards are promised to have concentration FYI) because success means I invalidate all of their wizard levels for 30 seconds. 30 seconds they have -10 ac, a d4 hit die, and 100% spell failure while I lay down about 30 attacks by the time that's over... Unless, you know, I reapply it and they aren't already dead. Now you might be thinking of a PvP situation and while you'd be correct I would also start applying this in PvE as much as I can now because I'd be invalidating scary wizard NPCs that probably aren't going to get re-adjusted across the board for this. So if they did implement it, the developers would also have to debate whether or not they want to spend a day off fixing every single wizard mob and rebalancing dungeons.
Sorry it's a bit lengthy but I hope it gives some insight and you could see the other side of the proverbial aisle.