I see people confusing the Guildwars 2 dynamic event system with Firefall's. They were very different. GW2 had fixed locations. Firefall was fully dynamic in location. The full system was supposed to also vary the nature of the encounter depending on time and location. Different things were supposed to spawn based on location or on time of day. Also when 2 dynamic events spawned near each other, you got emergent gameplay (like Nados going after Thumpers). Also, these events were supposed to be hooked up our our AI Director which was designed to manage the pacing and flow of dynamic events to players..and never implemented.
As for ARES missions, they were not dynamic events in the original sense of what I wanted.
No open world online game has done this, and Firefall never finished it. Ember will.