They are a rare drop and noticing that your highest light right now is 386 I would say that you playing non-stop is a lie.
Do Normal Siva Strikes instead of heroics, they are easier and faster. I did 20 for the record book and ended with 5 keys in my inventory when I was done.
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25 abomination strikes for thorn bounty no key ... lets see if i am more lucky today
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Heroic Strikes drop up to 385... Then Exotics got him to 386