The only time my thumbs get tired is when I'm learning a move.
I think you're thinking about this a bit wrong. Using the term 'necktie' implies a significant tilt upwards, so that the top of the deck is parallel with your own body. Think of it more that the front edge of the deck is pointed at the eyes of the person across the table, and a little to the right (if the deck is your left hand). At least, that's how I do it.
This mimics the natural way I deal cards fair as well. I feel that's the most important thing - make it all congruent.
I know perfectly well what necktying is, but I have a problem with the statement that no one can ser the top card when you do it.