Looking at Rowdy in vanilla you do have a lot of Feats to play with. Stuff like Weakening Wound that's usually good isn't so much because stuff you hit will usually be dead. You can burn one Talent on Focus* but better save the Combat Trick for Shatter at eight (first time you qualify for it, and needed for things that show up then like Maugla). TTT can only get one Combat Trick, which makes more sense. That means Outflank at 7.
Thing is I really want to be Vital Striking to get the extra Sneaks instead of Cleaving so to get to Improved Cleaving Finish I'd be using four Feats I might not even want to pick up the chance to clear the board when I kill stuff. Undeniably powerful but not sure it's really solving the problems I typically need to solve since adds are rarely an issue. Theoretically Cleaving with Debilitating would be solid but then you're missing the Vital Strike.
How much the fewer skill points pinch (and not getting Stealth as Class Skill) depends on rest of party. I really like having Trickery, Perception, and Persuasion on MC (especially with TTT Trapfinding that boosts both Trickery and Perception) since that handles most of the situations where you're alone and you can turn on only skill checker gets experience to good effect. Also gives you a lot more flexibility with party makeup.
Persuasion feels bad since eventually Frightful shows up but a lot of the game happens before then. Being able to Intimidate anything on your first turn helps a lot on a class that is Two-handing with Light Armor (to avoid getting attacked) and relies on Shatter to land it's hits. Second turn move + Vital and slay. Unfortunately TTT requires a hit to turn on Shatter so that's a nonbo for me. Signature Skill mod does give Rogues free Signature skills and for Persuasion that turns on Thug ability if you win check by 10 or more. There's also a lot more to spend your Feats on.
As for Vanilla the Lead Blades Oread and Pitborn Tiefling give good bonuses (Tieflings get a good early ring to help with Stealth/Trickery too) for Rowdy but speed on the Oread and INT malus on Tiefling are tough**.
Good Vanilla Feats:
Intimidating Prowess
Improved Initiative
Combat Reflexes (non-casters in Light can get DEX up to a respectable level, Prereq for Seize) since you're going to hit hard with AoOs
Shake it Off
Blind Fight (*does* solve problem I need to solve like Nabasu Gazes and Displaced bosses/Votaries)
Skill Boosters like Persausive/Deceitful to take RNG out of Skill Checks
Medium Armor Proficiency
even the individual save boosters with Mythic that gives you advantage can be good
Then on modded you've got all kinds of good options.
That said can't say I blame you for picking up ICF, it's a nice effect when it gets there, just far from broken given the cost (including what you're doing to Sosiel). I just feel like I'd also want to be Vital Striking bosses and then if I'm triggering ICF I've already killed the boss so seems like win more. Maybe you whack the caster then that lets you clear out Rogues and Archers too which would be solid.
* - I really like Falchion for wider Crit Range plus ability to use Jinx and the one that kills stuff under 100 HP which seems good with Vital Strike.
** - you're pretty well set up to get Mobility reasonably high to ride Bismuth and use the Mounted Feats as well, helps with glass cannon problem. Can also cover Athletics if you've got the points.
Blight Fight, as I wrote earlier, is pointless, you quickly unlock the ability to use true sight.
The number of enemies it is really useful on is quite limited - this is not Kingsmaker.
In the case of Nabasu this is quite useless as death ward does not require a feat and works just as well. I would say it's even better.
The difference between light and medium armor is literally 2 AC, in the first act it is even less because at the very beginning you can get light armor +2 which is as good as practically most medium armors you have available in 1 act.
Even later, 2 AC is a dubious profit that won't help you too much against stronger enemies.
Combat Reflexes is very good, I would personally choose it as a second or third rogue talent.
Improved Initiative is always good, you still have so many free feats that you'll be able to pick it up early anyway.
Shake it Off is pretty good only you don't need it right at the start of the game. You have to select it on several characters, which means that you have to give up more important talents such as Slashing Grace on Camelia.
All skill focus stuff is good, it just doesn't give your character any meaningful combat bonus.
Persuasion would be cool if you could unlock dreadful carnage at level 10, but it comes too late to be useful.
This is not a kingsmaker where having high persuasion on the main character was practically required.
Using dazzing display or demoralize is completely unworthy on a non-charisma main character.
Seelah would be better if you want to use it.
Intimidating Prowess is okay if you are using this on a persuasive character, the problem is that Rowdy only gets 3 skill points per level.
Another thing is that it makes sense if you choose dreadfull carnage only that it unlocks only at the level at which your casters receive Frightfull Aspect
Wasting a turn trying to demoralize is a bit pointless. You have other characters that would be better suited for this and at the same time wouldn't waste a precious turn.
You still have a few low-level spells that work similarly.
Both Scare and Fear keep working even if the enemy defends himself.
By the way, scare is suspiciously effective against a vescavor, even without investing in necromancy it almost always works for a swarm.
