Mox, you have just been very unlucky...
With that many points you should be in the pool for most of the artifacts. There are still plenty (over 30) artifacts in the 250 - 1000 range... Even more at higher ranges.
Eliminating the lower artifacts from the loot table is not an option - it would dramatically lower the rarity of the higher artifacts. They are meant to be rare. You shouldn't expect to get one just because you have lots of points.