"Stakes suitable for very, very hard compacted dirt surface. "
"I've heard great things about ground hog stakes, but @ .7oz/stake, that's too heavy."
If it is just compacted dirt, and No rocks, then Ti needle stakes will work and are probably the lightest option. It's the embedded rock/gravel in the compacted matrix that present the problem. The physics of pounding something into "nature's concrete" is demanding and not easily circumvented.
The Vargo UL Ti Nail that you reference will bend/break at the eye if hammered to hard.
The other Vargo Ti Nail has a stated weight of 0.6 oz, but after adding a the cord loop Required to pull them from hard ground, it is closer to 0.7 ounces.
If you are concerned about the weight difference, use needle stakes and bury the stakes under rock piles for the "impossible" sites. More time, but less weight.