De-esssss

Isolate the offending sibilant syllables as separate clips.
You can then apply a specific "De-Ess" plugin or use an EQ to tame each one.
Applying a blanket De-Ess or EQ can make the vocal sound unnatural.
This process leaves the rest of the vocal untouched. 

Bash von Gitfiddle
I'm surprised this thread hasn't been moved to "hardware" or "techniques" now that it has been turned in to a "techniques" with "hardware" discussion. :-b

it's a dying forum, no-one can be arsed with that sort of thing any more

I like my NT1. Not so great on my male voice, seems overly harsh (could be just my voice though). Works well on female voices, sublime on brass/woodwind instruments where you can place the mic a little further away than with a vocalist. Can be a bit harsh on acoustic pianos and guitars though where some subtleties may wish to be recorded.
But to the OP regarding sibilance, I agree with those that are saying mic technique is a good start. Place the mic a little further away. I've also had success wrapping the mic in 4 to 6 inches of cotton wool, then placing a good pop filter in front. This also relates to the previous sentence, as it keeps the vocalist further from the mic.
Bitflipper has a point in using a dynamic mic, as these tend to pick up less of those pesky sss's, and if you get really close you still pick up the subtleties of the mouth/throat/tongue etc, and mic technique is also less of an issue. However, mic technique can become tricky, as you lose those subtleties if you have a softer voice and move off the mic even just a little.
So, can't go past a good quality capacitor mic. Comes down to good engineering practice by the sound recordist, good mic technique by the vocalist, and good post production by the person doing the mixing.
 
Any good EQ, compressor, or de-esser can work wonders. But, if you want the best results, you will need to use these independently on each instance of the offending words. I can't stress this enough, you can set a catch-all setting on a good de-esser, but you won't get the same results every time, as each word is sung differently depending on what part of the vocal range the singer is in, what words or breaths have come before it, and how the singer is using the microphone at that exact time the word is sung.
Hope this helps.
P.S. I've used the VX64 quite a bit over the years, but never for the de-esser as a de-esser.