I don't agree with that. If someone is turtling, that means he's trying to defend himself. A good melee player should be able to take advantage of this naturally (unlike you). Because in the end, the offense and initiative matters so much in a duel. You'd want to force your opponent to the defensive stance, so you can put the pressure on him much easier. If he's turtling, that means he gave you the advantage anyway; unless he's trying a different tactic (that's arguable a bit, but still you have the upper hand). Many good 2hers and polers are doing this, so in the end this is their advantage towards shielders when it comes down to melee. The comparably difficult timing of defending with a shield, low reach, low damage and lesser movement speed is the disadvantage of shielders towards other classes.
In the case of a swashbuckler, they can still get spammed by 2handers and polers; because of the short range. But now since they have better stats than a shielder and are now moving much faster without the weight penalty of the shield; they have other advantages as well as nudges. The advantage of swashbuckler is, they have the same reach and damage; but better mobility and stats compared to shielders. Without the difficult timing of the shield, they should be able to take the initiative against them. Against 2hers and polers, well they have nudges now. So nudge is not really needed against a shielder, but more needed against 2her and polers (mostly because of their S key and kick tactics).
Enjoy your -1 zlisch.