The dual wielder feat really opens up your combat options, especially for assassin builds since you can now use those bigger weapons in both hands. Most people dont realize you can actually run around with two rapiers or longswords which is pretty great for damage output, and you get a nice defensive boost with that +1 to armor class while dual wielding.

Something worth noting though, if youre looking to add your ability modifier to off-hand damage rolls youll need the two-weapon fighting style from either fighter, ranger, or college of swords bard, as the feat itself doesnt cover that. The real value comes from being able to mix and match different weapon effects, like having a poison blade in one hand and maybe a silencing weapon in the other, while still keeping your bonus action free for all those sneaky rogue moves.

The nice thing about this setup is how it works with other class features, so you can still use stuff like cunning action without running into timing issues. Just keep in mind that while the extra weapon options are great, some builds might get more value from pumping ability scores or grabbing something like savage attacker if pure damage is what youre after.