Events and medals are getting goofy
If you stay to kill a single champ you’ll end up with bronze, if you run around and hit whatever you can hit you’ll more likely hit gold.
Plus, it seems to matter what stats you use – plus weapon. It’s better to have a ranged weapon to run less and hit more, and then, it does make a difference if you’re on power based stats or rather on condition or something else. If something dies too soon, conditions doesn’t get the chance to deal ‘the real damage’ for example. For power (plus precision) based stats you deal more damage, which is no secret.
Haven’t had a problem on DS at all, I always hit gold, but I’ve never been there with anyone else than my soldier Necro or valkyrie Ranger.
As for Tequatl’s battery phase, going there in carrion stats results in bronze, hardly silver, going there in soldier’s, zerk or valkyrie results in guaranteed gold.
So I don’t think it’s random at all, it may just scale the needed damage for each rank with duration and participation in the certain event.