Game Mechanics: Super close range mob leashing in Burning Woods

[hala745]

Friend was swarming in burning woods, noticed some really weird things. Mobs will completely de agro after a set period of time, even super close range. Video posted to show this happening. https://www.youtube.com/watch?v=X3G9yFgvKcE
Timestamps- 21 seconds first skeleton de agro, I target him showing 100% hp (not low hp runner)
56 seconds two mobs de agro, one actually agros my character which was not on its agro list previously
1:12 at this point many mobs start de agroing.
New custom EQ feature? This has happened many pulls, not a one time occurrence