Tell that to the gun which fires healing syringes that can travel from one end of the map, hahah. Or the flamethrower which actually can toss fire from a ridiculous distance.
Not to mention, when you can strap a rocket launcher and chain-gun on a giant who can cloak. I'm pretty sure you're up there with "Hi-tech" .
The range of such darts is a developping oversight - maps are short enough to ignore gravity action for small projectiles.
As for the magically-healing darts (and syringe), I think Undedd's explanation is the best: Syringes have healing nanomachines in them. This may be a little farfetched, but it's the best us players could find.
TWI strives for realism in OUR weaponry. If you think, even the regular clot is too technologically advanced. We are able to clone stuff, but only non-alive things. And live beings suffer from "old" diseases: their cells are at the same time as old as the living being itself and the cloned being.
Adding these futuristic weaponry will break this.
That, and they don't have any real though in them. This is just an excuse to put a tesla weapon and laser rifles in the game.