This gives me an idea. I don’t want to make the reaction be the same as deflect Missiles, but...maybe am opposed attack roll. If you hit, their attack misses. If you beat them by...5 or more, you hit them? Idk, I think there is something there.
I like that the Defensive Duelist feat can simulate a main gauche, and does not require a high Dex score to be useful.
Your proposed version of the feat,
doc, is going to favor characters that specialize in melee attacks. It also will synergize nicely with the Shadowblade spell. Might as well change the Feat name to Arcane Trickster's Defensive Duelist Feat.
This is not to say, I don't like your proposed changes as a design space.
Granted, it is free (no spell slots, etc.) but is only against a single attack. If it fails to help, the reaction is lost.
dnd4v, I think we differ in weighing the value of an
at will Reaction via the Defensive Duelist feat versus the use of a spell slot and Reaction through the Shield spell.
A Shield spell that fails to foil a hit,
costs a 1st level spell slot, and expenditure of one's Reaction.
The Defensive Duelist feat just costs you the Reaction. Opponents not triggering Opportunity Attacks is not uncommon, in my experience. When a 4th level character will be brought to 0 HP by 4 successful attacks from a giant spider, negating
any hit is more impactful then an Opportunity Attack with a dagger for 1d4 + 4 damage.
I guess that is the reason this feat isn't popular for rogues, who already have something they can do with their reaction under the same circumstance,
The difference is between the
likelihood of the AC bonus from DD negating the hit or not.
Having the option to
either use Defensive Duelist or Uncanny Dodge is not a bad place to be in. Uncanny Dodge is more generally applicable, but the DD feat, especially in conjunction with spells like Blur, Mirror Image, or Greater Invisibility is no slouch.
+6 to AC while the opponent has Disadvantage on a melee attack roll, is very effective on a high level Arcane Trickster.