Sorry if this has been suggested already...but I think that in order to keep old content such as this and Hydra alive, and to help out newer people, they should add these (maybe other stuff too?) to the list of additional ways you can earn tombstones after 2.1

It can be sort of like the Guildhests where it checks "1 or more players has not completed this" and if so you earn tombstones. That way people aren't just running hyrdra/chimera nonstop for easy stones - there has to be someone on the quest in order to earn anything. Kinda win-win; people get help, and the helpers get rewarded.