Hi,

I m building a Human Thief Rogue, 17 DEX and 16 CON on Lv 4, Tough and Lucky Origins, no multiclassing. He is more in melee than ranged and has mastery with Daggers and Short Sword. He uses his bonus attack for stuff like Manacles, Ball Bearings etc.

On level 4 I want to round DEX to 18 - what is the best mechanical feat for a melee based Rogue?

Sentinel/Zhentarim Tactics for offturn attacks? Defensive Duelist for more AC? Mage Slayer for saving throws? something else?

Only 5.5e feats of course, no legacy or 3rd party.

THX

You can't take rent due to requisites. So sentinel is best.

Honestly I would go for assassin or phantom if you want to be melee. The extra nova damage is nice

Dual wielder at level 4, allows you to make another offhand attack in addition to the one from nick.

8 17 16 10 14 8

At level 1 take tough and planar pact infernal pact

You can hit once with your Shortsword and twice with your daggers or a Scimitar. That is 3 chances to land sneak attack. At level 8 +2 Dex and at level 10 take Infernal Bulwark +1 Con, and at Resilient con +1 at level 16 take Speedy and at level 20 take boon of combat prowess

You final stats are:

8 20 20 10 14 8

You have an AC of 20 resistance to fire damage, proficiency in wisdom, charisma, intelligence, dexterity and constitution saving throws have evasion, three attacks, uncanny dodge 243 HP attacks and 30 foot darkvision that can see through magical darkness.

Assassin is so bland and Phantom only gez interesting after lv 9 imo. also I cannot get dnd beyond drops

If you using hit and run tactics I.e. lots of Disengages and Dashes then Charger could be an interesting choice.

- Ability Score Increase. Increase your Strength or Dexterity score by 1, to a maximum of 20.
(So you get your 18 Dex.)

-Improved Dash. When you take the Dash action, your Speed increases by 10 feet for that action.
(You can get a extra mobility for targets just that little bit out of reach.)

-Charge Attack. If you move at least 10 feet in a straight line toward a target immediately before hitting it with a melee attack roll as part of the Attack action, choose one of the following effects: gain a 1d8 bonus to the attack's damage roll, or push the target up to 10 feet away if it is no more than one size larger than you. You can use this benefit only once on each of your turns.
(Damage boost and a free knock back for battlefield control)

If you are set of thief a fun/debilitating option you have is to use a net with your attack action then your bonus action to utilize and tie a creature up with rope/chain. You can take the street justice feat to improve the rope/chain DC.

I cannot officially recommend it but there is always the option a rogue would take. Stealing feats is what my character would do.

That is something I definitely plan to do, especially if I m at disadvantage and cant use sneak attack.
If the +2/+3 from street justice is worth it though, I m not sure

stealing what?

The drops from sources that aren't WoTC.

not to mention, that last bit (pushback) could be excellent setup for a Cloud of Daggers trap or Ensaring Strikes

I would not take zhent chain, it’s a trap. Honestly I would skip tough and take magic Initiate wizard for booming blade instead. Probably also switch to arcane trickster. Booming blade plus cunning strike disengage is a lot better than dual wielding. Nick is just annoying on a rogue because it breaks your vex chaining and isn’t worth using. Frankly a 1 lvl fighter dip for shield prof and defense style is really good so your AC isn’t shit, then you can stack defensive dualist as well and actually not crumple like wrt tissue paper in melee. If you don’t do that then a dual wielding melee rogue is just a liability to your party unless you go out of your way to skirmish and stay as far from enemies as you can.

Does Sentinel really proc much on a rogue? I would think enemies would just attack the rogue. If you're next to an AoE they would be able to leave the AoE and stay within range of the rogue typically. I get getting extra sneak attacks, I just haven't seen it successfully used.

I cant take BB as it is legacy I m affraid...
and I cant multiclass either. why a liability?

Because you’re a squishy target that will likely go down in 2-3 hits then your party will have to waste resources healing you. You’ll have 15 to 16 AC in studded, that’s not enough to mix it up in melee. Rogue is probably the weakest class in the game and melee dual wield rogue probably the worst general way to play it generally.