Originally Posted by
MadFloyd
OK, I got the whole story now.
Yes, it was changed with Update 9. It used to apply an 80% slowdown to both players and mobs, but it was decided at that time that it was too close to a root.
It's currently at 40%. I just sat with the entire systems team and verified that it is indeed a 40% slowdown. Apart from it technically moving the mobs at 60% of their normal speed, it visually looks like they are moving at 60% of their non-slowed speed. This is the same for players and monsters (i.e. before Update 9 players affected by fog would have moved twice as slow as now).