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The chance is 1:200 so the expected result from 800 would be 4 gold tempers. Getting zero is slightly unlikely but not inconceivable. Someone much better at the maths could likely tell you the exact odds of getting zero tempers from 800 raw mats, but I suspect it's not as low as you think.
You did get 7 tempering alloy from an expected result of 5 if that makes you feel better so you did well on that side.
Plentiful Harvest is a chance to pull double yield from a resource node out in the wild. It has no affect on extraction The Devs told us way back in Beta, the only thing that increases your extraction chances are the Extraction passives in the skill lines.