Game Mechanics: Flash of Light causes fleeing mobs to warp uncontrolably.

[kaev]

Since the last patch (or maybe two patches back) something similar occurs occasionally with non-blinded mobs. The client shows the mob fleeing in a particular direction, after a few steps the mob will warp to a position the fits with it fleeing in a direction 90-180 degrees different from the mob's facing. This will repeat until you root the mob or kill it with ranged attack (very difficult to get melee damage, basicly you have to be waiting at the warp-to loc and swing when the client & server sync the mob location.)

Seems likely to me that this is the same thing the OP is seeing with Flash of Light (I quit using Flash of Light some time ago because of bizarre pathing/aggro shit creating trains when engaged mobs would take off running because somebody not at the top of the aggro list happened to move to a location with bugged pathing.)