For cases like Dolmens, Geysers, and maybe Harrowstorms there is always one active somewhere in that zone and at the very least, Dolmens follow a pattern so it may just be no one is doing the other zone dolmens so others cant activate.
I'm not talking about Dolmans, they respawn every 10-15 mins as far as I can tell.
Are you meaning Dark Fissures? If so I guess that could be the reason but then again I would think they are on a simple respawn rate system as well.....
It's only really Harrowstorms/fishing spots that have special circumstances.