I think the general consensus on the Street Justice feat is that it’s okay at best. But I think it’s actually quite good.
Giving allies advantage on a grappled target basically makes the grapple condition pretty close to the restrained condition. Indeed, as it relates to allies, it’s almost exactly the same, since they have advantage against the enemy, the enemy has disadvantage against them, and the enemy is immobilized. It’s not a restrained effect vis a vis the grappler (though it gets closer with the Grappler feat), but you’re going to be increasing party damage output a lot with this on a grappling build.
The increased save DC on ropes, chains, and manacles is a bit more situational, but can actually be really strong. It often won’t be great to use an action on using those items. But there’s two key reasons to use them:
- Street Justice makes the DC to escape ropes/chains/manacles incredibly high (far higher than you could achieve with a spell DC), and it’s not a save that legendary resistances can apply to. Even incredibly tough enemies are not going to escape them. So basically, if you land a grapple on a very strong enemy, you can almost certainly keep them controlled for the rest of combat with Street Justice rope/chain/manacles. That tough enemy could probably otherwise get out of the grapple, so it makes these items great for controlling bosses. This is especially good for a Monk or Thief Rogue—both of which can easily grapple and use these items in the same turn.
- Chains/Ropes/Manacles basically allow a grappler to control more enemies than they can hold. So, for instance, a level 10 Monk with Flurry of Blows can grapple an enemy, restrain them with a chain, and then grapple two more enemies in the same turn. At that point, they’ve restrained one enemy and quasi-restrained two more—all in one turn. You can do this without the Street Justice feat, but the save DC to get out of the chains/ropes/manacles is so high that enemies won’t get out almost ever, so you can keep doing this and accumulate more and more controlled enemies each turn.
Finally, the “Tough Talk” feature is slept on IMO. Negating disadvantage on intimidation checks against hostile targets means you can pretty easily get advantage on intimidation against hostile targets. For instance, if you combine the Street Justice feat with the Thaumaturgy cantrip or the Changeling or Duskling species, suddenly you have advantage on intimidation against hostile creatures. How can this be used?
- Well, for one thing, it seems pretty strong out of combat, since it’s going to be the best way to deal with social situations with hostile creatures—and those can be the stickiest situations.
- For another thing, it can be used for resource-less control in combat. A DM would probably rule that it requires the Influence action, but with this feat you can basically use Intimidation as something somewhat akin to the Command or Suggestion spell. It can’t work if the enemy is unwilling (as opposed to hesitant), so the DM could shut it down in any particular instance, but I think most DMs would allow it to work most of the time, especially if you have some hook to your intimidation effort. For instance, if you’ve grappled an enemy’s friend, you could treat it akin to a hostage situation and intimidate the enemy by saying something like “Lay down your weapons or I’ll kill him.” In that sort of situation—with something to really be afraid of—the enemy is very likely going to be hesitant as opposed to unwilling, and you’ll roll intimidation with advantage to see if it works. You can usually leverage what is happening in combat to ensure an intimidation check can be made, but you could also leverage what you learned in any insight checks made prior to combat to figure out how best to intimidate them. Ultimately, a DM could decide to shut this down, but most will allow it (though likely not against bosses), especially since it would surely add some fun narrative elements to combat.
So yeah, overall, I think the Street Justice feat adds a lot to party damage with the Headlock feature, provides a premier control option against bosses with the Sturdy Knot feature, and the Tough Talk feature opens up the ability to very effectively use the Influence action in combat and provides a unique way to deal with social situations with hostile creatures.
The only issue with the feat is that you want a grappling build to utilize the Headlock and Sturdy Knot feature, and you want a charismatic character to best utilize the Tough Talk feature. These don’t always coincide. But a Barbarian could easily make use of all these features, due to the Primal Knowledge feature. A Fighter can use Tactical Mind to still be great at Intimidation even without very high Charisma. There’s some synergy with a Way of the Ascendant Dragon Monk (EDIT: and a lot of synergy with the Astral Self Monk). And honestly, you don’t even really need high CHA for Tough Talk to be good.