How to Deal with Startling Shot?

[Weaker Ink]

We're near the end of our campaign and all of my player's Fated characters are basically unstoppable for one reason or another (as should be with a long running campaign). However, there's one talent specifically that's giving me a lot of problems as a Fate Master. One of the Fated is a maxed out Marksman with a very good Long arms skill (AV of 7) and the Startling Shot talent from the Marksman pursuit. The talent reads as such, found on page 119 of Above the Law:

 

Quote

When the character declares a Long Arms attack against a target, she may discard a card and declare that she is making a Startling Shot. If she does so, she makes the attack against the target's Willpower, rather than its Defense. On a successful hit, the attack deals no damage to the target, but this character still makes a Damage Flip.

If the attack would have dealt Weak damage, the target becomes Slow.

If the attack would have dealt Moderate damage, the target becomes Paralyzed.

If the attack would have dealt Severe damage, the target becomes Paralyzed and must immediately make an Unconsciousness Challenge with a TN equal to the final duel total of this attack.

 

The issue I'm running into is that the character's Long arms skill is high enough that they regularly get their damage flips to a straight, then cheat in a severe for damage. Then the TN for the Unconsciousness challenge is so high that it's nearly impossible for any Fatemaster character to pass (TN between 18-21). It's completely blowing out any encounters I have planned and even Master level enemies are getting knocked out as soon as the fight begins. The character has also picked up a couple steps in Wastrel to ensure that card flow is consistent. 

Is there a way that I can balance this ability without the player feeling like I'm taking away a powerful skill? I don't want to completely nerf the character but with the ability as is there's just no real threat in fights anymore and I'm concerned that it's taking the tension and fun away from encounters.

 

Follow-up question: What's your ideas in regards to Startling Shot and special ammo? RAW the ability implies that Cavity bullets should still allow for a  on the damage flip against unarmored targets but the flavor of the ability is more about startling the target by firing near them, not hitting them. In which case, the type of bullet shouldn't have any impact on the damage flip?

[Shadowopal]

My answer to long arms is more targets. If the character/party has advanced that much, most likely s/he had made a name for themselves. Smart npc's will get word that the character/party is on their tail and have more support to deal with them. A couple of hand to hand thugs in hiding can jump the player and stop the long arms nonsense for at least a turn. 

 

If they took out a big bad, maybe a Shaman with healing or a necromancer was hired. Big bad jumps up and pays the character a visit while s/he is distracted with the hand to hand thugs. 

[Hellomurse]

Toss something at them that is immune to Willpower Duels. If you can't find a suitable pre-existing one make it up, or modify one.

Engage the characters by a mob(friendly or hostile)/swarm/thugs on all sides.

Frozen Heart prevents Paralysis.

Just a couple of suggestions. Hope these help.

[Steamtastic Vagabond]

You could use Undead or Constructs as those things are basically immune to unconsciousness.