We get GC Seals instead of gemstones at lower levels and those have rewards.

Gemstones and hunt currencies having the same rewards would make people choose the easiest option and potentially obliterate the hunt community. There was a time when I was worried they'd discontinue hunts because hardly anyone did them. Once hunt trains took off and they added a mount grind, hunts were saved. They are big because of the rewards.

50,000 uncapped tomestones farmed via dungeons that are the same every single time. I don't think that would be good without addressing how much the same they are.