Is there anything that can get rares to come more often, or is it purly random? Does your harvesting skill level in that teir make a difference? eg. the higher your skill the better the chance of getting rares
Having a harvest skill significantly higher than that required for the tier you are harvesting does increase your chance of a rare harvest, but the increased chance is so small as to be unnoticable. Its all down to that streaky random number generator. It does help to use the best harvesting tools you can, just because the decreased time it takes to harvest each node means you can hit more in the same time period.
For more detail check out A Harvester's guide at Zam Check the Note on rares section. There is also a fairly recent post around here from Domino about the rate changes between tables. (its in a long thread about +harvesting skill on gear)
