As far as I understood, they're trying to make DD a dueling spec but it is highly improbable to make a dueling spec without adding sustain and protection (which thieves should not have). I am suggesting some additions to swipe and some changes to traits to make daredevil a close quarter fighter that is based on evades and finding weakness.
Keep swipe as it is with 600 range but add a second skill that replaces swipe when swipe is used:
Swipe ===> Exploit : Starts in CD (same as swipe), when activated, for 5 seconds gain %10 damage and damaging skills gain 100 range and are "unavoidable"(ignores evade) against your target.
If you go farther than 600 range to your target after using swipe, Exploit skill reverts back to swipe with remaining CD. Exploit is affected by talents that affect stealth.
Now to the traits:
Switch "Weakening Strikes" with "Marauder's Resilience".
Rework "Marauder's Resilience": Power to Vitality conversion is a joke. Instead gain an addition %20 damage reduction for 2 seconds against the attacking target when you succesfully evade an attack. (Foe must be within the range threshold)
Nerf "Staff Master" power gain to 100 and an additional 100 when wielding staff.
Now these changes enables thief to stay in the fight while preventing the in and out playstyle as a tradeoff. Main mechanic here is "Exploit" and you should stay in range to be able to use it as a burst ability.