Unlike Sneak Attack or Trick Attack, Feint still remains active despite missing. As long as a hit is landed (even for zero damage) within 1 minute of activation, Feint's evasion down effect will apply. It will also stick even if your attack is countered.
The initial effect of Feint is -50% evasion.
The effect of feint decreases over the course of its 30 second lifespan. In testing, it's been seen that tested mobs have gone from conning low evasion at the beginning of feint, to high evasion by the end of feint. This means that the decrease in potency from beginning to end is at least 40 evasion, if not greater. Test link is included in the discussion section.
The effect is not applied when a Weaponskill is used - it is applied with the next regular melee hit. It also is not applied via ranged attacks.
Will replace any additional effect on the hit applied on, including Enspell magic and Samba effects.