I guess I'll just echo what's been said here.
Provoke doesn't work in FATES. Maybe what you saw was the boss already moving away from her intended area and someone vainly using Provoke, to try and bring her back.
Even if it worked and someone used Provoke, then whoever was trying to grieve, would have to keep hate on boss by constantly using Shield Lob/Tomahawk, to kite her out of the intended FATE area, or constantly using their combos while kiting, which is difficult to do.
I've seen it happen many a times when FATE grinding was hype for leveling. Even if there were no other FATE's popped up, people would teleport/leave the FATE area before the boss was dead. Then boss would randomly target someone with Void Fire spells whether they're in the area or not, as long as they engaged her at some point. Same thing would happen to Steropes. The only thing is, you don't know who the culprit is because it doesn't show who she randomly targets to cast Void Fire.
