Nope, no bug. They're [i][u]insanely[/u][/i] rare as public events.
Check out this app: Events for Destiny Track Public Events Timers by Ruben Frosali
https://appsto.re/us/eDA82.i
My only other advice would be have a friend join you in a Fireteam and both of you sit in the different zones it can spawn in. When an event occurs, either of you can say whether or not it's a WARSAT and join the other.
English
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While using this event tracker be warned that the events sometimes dont prock till -6 minutes on the timer and sometimes they are on time