That's kind of how it was in D1. You pop 3oC kill boss. If an exotic doesn't drop then your chances keep going up each time you pop 3oC until you get an exotic. Then your chances are reset. I would grind heroic strikes and get an exotic to drop every 5 or 6 strikes.
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From a coding perspective it's the only alternative I can think of other than a flat increase to drop rate. I'd say it's 50/50 that it works that way.