I've had a grand total of 1 drop for me, and that was about 2 weeks ago. That's not including the 3 I got for Shiros quest (one on each character). I understand that it's RNG but I'm hearing that my experience is the norm.
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I've noticed the same thing. I was running siva crisis strikes for vanguard/dead orbit rep in hopes of getting a key, but finally decided it wasn't worth the hassle to do the strikes. It's faster running patrols for the rep and since I wasn't getting keys there wasn't any reason in running the siva crisis strikes. Once I hit 390 there is even less reason to do the strikes. I hope they increase the drop rate.