GS banishes mobs at random
Did you possibly level up during the fighting?
From the wiki : Leveling up
When a character levels up, they are fully healed, they gain full adrenaline and life force, and they launch and damage all nearby foes.
No I wasn’t leveling up. This is why I post here, because it happened twice in the same day and is definitely unnatural. I’ll keep at it and try to see if I can reproduce it.
Sounds like levelup to me. You can still get levelups after 80 in case you didn’t know. It happens sometimes with me too and always catches me by surprise. One time it actually saved me; an elite risen illusionist got interrupted right when it was about to chaos storm me. :>