Hey, I know I'm coming into this way after everyone else stopped discussing it but I want to say my piece anyway.
I agree with most other replies. The potential of Sand Mastery has not been fully explored. In fact, a key part of Kenton's character arc was that his potential was supposedly limited. I would LOVE to see what a skilled Sand Master could do if they were powered by Dor.
The point I want to make however is that looking at the above comment I see a basic premise.
If the things magic can do can be replicated by technology, the magic system is therefore lame, redundant, or not special in some way.
If this was not what you meant I apologize, but it's what I hear when I read the above questions.
I find myself disagreeing with this premise.
Spoilers for Mistborn
There's also the point that the Sand Masters were a culture more so than a military. Sand Mastery to them was not a way to fight or save lives, it was an art form. A source of competition. Skill in Sand Mastery was source of pride, not intimidation. Even if technology on Taldain advanced to a point that Sand Mastery became completely irrelevant, which it seems like it may have, I suspect many would still practice their tradition. Not because its useful, but because, to them, its beautiful.
I also think Sand Mastery is very cool